Acceptor Percolation Determines How Electron-Accepting Additives Modify Transport of Ambipolar Polymer Organic Field-Effect Transistors.

PubMed

Ford, Michael J; Wang, Ming; Bustillo, Karen C; Yuan, Jianyu; Nguyen, Thuc-Quyen; Bazan, Guillermo C

2018-06-18

Organic field-effect transistors (OFETs) that utilize ambipolar polymer semiconductors can benefit from the ability of both electron and hole conduction, which is necessary for complementary circuits. However, simultaneous hole and electron transport in organic field-effect transistors result in poor ON/OFF ratios, limiting potential applications. Solution processing methods have been developed to control charge transport properties and transform ambipolar conduction to hole-only conduction. The electron-acceptor phenyl-C61-butyric acid methyl ester (PC 61 BM), when mixed in solution with an ambipolar semiconducting polymer, can reduce electron conduction. Unipolar p-type OFETs with high, well-defined ON/OFF ratios and without detrimental effects on hole conduction are achieved for a wide range of blend compositions, from 95:5 to 5:95 wt % semiconductor polymer:PC 61 BM. When introducing the alternative acceptor N, N'-bis(1-ethylpropyl)-3,4:9,10-perylenediimide (PDI), high ON/OFF ratios are achieved for 95:5 wt % semiconductor polymer:PDI; however, electron conduction increases for 50:50 and 5:95 wt % semiconductor polymer:PDI. As described within, we show that electron conduction is practically eliminated when additive domains do not percolate across the OFET channel, that is, electrons are "morphologically trapped". Morphologies were characterized by optical, electron, and atomic force microscopy as well as X-ray scattering techniques. PC 61 BM was substituted with an endohedral Lu 3 N fullerene, which enhanced contrast in electron microscopy and allowed for more detailed insight into the blend morphologies. Blends with alternative, nonfullerene acceptors further emphasize the importance of morphology and acceptor percolation, providing insights for such blends that control ambipolar transport and ON/OFF ratios.

Contrasting performance of donor-acceptor copolymer pairs in ternary blend solar cells and two-acceptor copolymers in binary blend solar cells.

PubMed

Khlyabich, Petr P; Rudenko, Andrey E; Burkhart, Beate; Thompson, Barry C

2015-02-04

Here two contrasting approaches to polymer-fullerene solar cells are compared. In the first approach, two distinct semi-random donor-acceptor copolymers are blended with phenyl-C61-butyric acid methyl ester (PC61BM) to form ternary blend solar cells. The two poly(3-hexylthiophene)-based polymers contain either the acceptor thienopyrroledione (TPD) or diketopyrrolopyrrole (DPP). In the second approach, semi-random donor-acceptor copolymers containing both TPD and DPP acceptors in the same polymer backbone, termed two-acceptor polymers, are blended with PC61BM to give binary blend solar cells. The two approaches result in bulk heterojunction solar cells that have the same molecular active-layer components but differ in the manner in which these molecular components are mixed, either by physical mixing (ternary blend) or chemical "mixing" in the two-acceptor (binary blend) case. Optical properties and photon-to-electron conversion efficiencies of the binary and ternary blends were found to have similar features and were described as a linear combination of the individual components. At the same time, significant differences were observed in the open-circuit voltage (Voc) behaviors of binary and ternary blend solar cells. While in case of two-acceptor polymers, the Voc was found to be in the range of 0.495-0.552 V, ternary blend solar cells showed behavior inherent to organic alloy formation, displaying an intermediate, composition-dependent and tunable Voc in the range from 0.582 to 0.684 V, significantly exceeding the values achieved in the two-acceptor containing binary blend solar cells. Despite the differences between the physical and chemical mixing approaches, both pathways provided solar cells with similar power conversion efficiencies, highlighting the advantages of both pathways toward highly efficient organic solar cells.

Multiplexed interfacial transduction of nucleic acid hybridization using a single color of immobilized quantum dot donor and two acceptors in fluorescence resonance energy transfer.

PubMed

Algar, W Russ; Krull, Ulrich J

2010-01-01

A multiplexed solid-phase assay for the detection of nucleic acid hybridization was developed on the basis of a single color of immobilized CdSe/ZnS quantum dot (QD) as a donor in fluorescence resonance energy transfer (FRET). This work demonstrated that two channels of detection did not necessitate two different QD donors. Two probe oligonucleotides were coimmobilized on optical fibers modified with QDs, and a sandwich assay was used to associate the acceptor dyes with interfacial hybridization events without target labeling. FRET-sensitized acceptor emission provided an analytical signal that was concentration dependent down to 10 nM. Changes in the ratio of coimmobilized probe oligonucleotides were found to yield linear changes in the relative amounts of acceptor emission. These changes were compared to previous studies that used mixed films of two QD donors for two detection channels. The analysis indicated that probe dilution effects were primarily driven by changes in acceptor number density and that QD dilution effects or changes in mean donor-acceptor distance were secondary. Hybridization kinetics were found to be consistent between different ratios of coimmobilized probes, suggesting that hybridization in this type of system occurred via the accepted model for solid-phase hybridization, where adsorption and then diffusion at the solid interface drove hybridization.

Solution-Processed Donor-Acceptor Polymer Nanowire Network Semiconductors For High-Performance Field-Effect Transistors

PubMed Central

Lei, Yanlian; Deng, Ping; Li, Jun; Lin, Ming; Zhu, Furong; Ng, Tsz-Wai; Lee, Chun-Sing; Ong, Beng S.

2016-01-01

Organic field-effect transistors (OFETs) represent a low-cost transistor technology for creating next-generation large-area, flexible and ultra-low-cost electronics. Conjugated electron donor-acceptor (D-A) polymers have surfaced as ideal channel semiconductor candidates for OFETs. However, high-molecular weight (MW) D-A polymer semiconductors, which offer high field-effect mobility, generally suffer from processing complications due to limited solubility. Conversely, the readily soluble, low-MW D-A polymers give low mobility. We report herein a facile solution process which transformed a lower-MW, low-mobility diketopyrrolopyrrole-dithienylthieno[3,2-b]thiophene (I) into a high crystalline order and high-mobility semiconductor for OFETs applications. The process involved solution fabrication of a channel semiconductor film from a lower-MW (I) and polystyrene blends. With the help of cooperative shifting motion of polystyrene chain segments, (I) readily self-assembled and crystallized out in the polystyrene matrix as an interpenetrating, nanowire semiconductor network, providing significantly enhanced mobility (over 8 cm2V−1s−1), on/off ratio (107), and other desirable field-effect properties that meet impactful OFET application requirements. PMID:27091315

Electrodialytic in-line preconcentration for ionic solute analysis.

PubMed

Ohira, Shin-Ichi; Yamasaki, Takayuki; Koda, Takumi; Kodama, Yuko; Toda, Kei

2018-04-01

Preconcentration is an effective way to improve analytical sensitivity. Many types of methods are used for enrichment of ionic solute analytes. However, current methods are batchwise and include procedures such as trapping and elution. In this manuscript, we propose in-line electrodialytic enrichment of ionic solutes. The method can enrich ionic solutes within seconds by quantitative transfer of analytes from the sample solution to the acceptor solution under an electric field. Because of quantitative ion transfer, the enrichment factor (the ratio of the concentration in the sample and to that in the obtained acceptor solution) only depends on the flow rate ratio of the sample solution to the acceptor solution. The ratios of the concentrations and flow rates are equal for ratios up to 70, 20, and 70 for the tested ionic solutes of inorganic cations, inorganic anions, and heavy metal ions, respectively. The sensitivity of ionic solute determinations is also improved based on the enrichment factor. The method can also simultaneously achieve matrix isolation and enrichment. The method was successively applied to determine the concentrations of trace amounts of chloroacetic acids in tap water. The regulated concentration levels cannot be determined by conventional high-performance liquid chromatography with ultraviolet detection (HPLC-UV) without enrichment. However, enrichment with the present method is effective for determination of tap water quality by improving the limits of detection of HPLC-UV. The standard addition test with real tap water samples shows good recoveries (94.9-109.6%). Copyright © 2017 Elsevier B.V. All rights reserved.

Vaccine perception among acceptors and non-acceptors in Sokoto State, Nigeria.

PubMed

Murele, Bola; Vaz, Rui; Gasasira, Alex; Mkanda, Pascal; Erbeto, Tesfaye; Okeibunor, Joseph

2014-05-30

Vaccine perceptions among acceptors and non-acceptors of childhood vaccination were explored. Seventy-two care givers, among them, acceptors and non-acceptors were interviewed in-depth with an interview guide that assessed vaccine acceptance, social and personality factors, and health belief model (HBM) categories in relation to oral polio vaccine (perceived susceptibility, severity, cost barriers, general barriers, benefits, knowledge, and engagement in preventative health behaviours). Community leaders were purposively selected while parents were selected on the basis of availability while ensuring the different attitude to vaccines was covered. Results showed that the HBM framework was found to be appropriate for identifying and distinguishing vaccine acceptors and non-acceptors. In addition, the HBM categories of benefits and susceptibility were found to influence oral polio vaccine acceptance. Second, the opinion of family members about the oral polio vaccine moderated the relationship between number of social ties and vaccine acceptance. Further, oral polio vaccine acceptance was related to outbreaks of paralysis of any sort, but not aggregate scores of other preventative health behaviours. Implications of this study include the investigation of vaccine acceptance in a high risk population. Research was done to investigate vaccine acceptance. Copyright © 2014 Elsevier Ltd. All rights reserved.

Spectrophotometric and spectroscopic studies of charge transfer complexes of p-toluidine as an electron donor with picric acid as an electron acceptor in different solvents

NASA Astrophysics Data System (ADS)

Singh, Neeti; Khan, Ishaat M.; Ahmad, Afaq

2010-04-01

The charge transfer complexes of the donor p-toluidine with π-acceptor picric acid have been studied spectrophotometrically in various solvents such as carbon tetrachloride, chloroform, dichloromethane acetone, ethanol, and methanol at room temperature using absorption spectrophotometer. The results indicate that formation of CTC in non-polar solvent is high. The stoichiometry of the complex was found to be 1:1 ratio by straight-line method between donor and acceptor with maximum absorption bands. The data are discussed in terms of formation constant ( KCT), molar extinction coefficient ( ɛCT), standard free energy (Δ Go), oscillator strength ( f), transition dipole moment ( μEN), resonance energy ( RN) and ionization potential ( ID). The results indicate that the formation constant ( KCT) for the complex was shown to be dependent upon the nature of electron acceptor, donor and polarity of solvents that were used.

Donor-Acceptor-Collector Ternary Crystalline Films for Efficient Solid-State Photon Upconversion.

PubMed

Ogawa, Taku; Hosoyamada, Masanori; Yurash, Brett; Nguyen, Thuc-Quyen; Yanai, Nobuhiro; Kimizuka, Nobuo

2018-06-25

It is pivotal to achieve efficient triplet-triplet annihilation based photon upconversion (TTA-UC) in the solid-state for enhancing potentials of renewable energy production devices. However, the UC efficiency of solid materials is largely limited by low fluorescence quantum yields that originate from the aggregation of TTA-UC chromophores, and also by severe back energy transfer from the acceptor singlet state to the singlet state of the triplet donor in the condensed state. In this work, to overcome these issues, we introduce a highly fluorescent singlet energy collector as the third component of donor-doped acceptor crystalline films, in which dual energy migration, i.e., triplet energy migration for TTA-UC and succeeding singlet energy migration for transferring energy to a collector, takes place. To demonstrate this scheme, a highly fluorescent singlet energy collector was added as the third component of donor-doped acceptor crystalline films. An anthracene-based acceptor containing alkyl chains and a carboxylic moiety is mixed with the triplet donor Pt(II) octaethylporphyrin (PtOEP) and the energy collector 2,5,8,11-tetra- tert-butylperylene (TTBP) in solution, and spin-coating of the mixed solution gives acceptor films of nanofibrous crystals homogeneously doped with PtOEP and TTBP. Interestingly, delocalized singlet excitons in acceptor crystals are found to diffuse effectively over the distance of ~37 nm. Thanks to this high diffusivity, only 0.5 mol% of doped TTBP can harvest most of the singlet excitons, which successfully doubles the solid-state fluorescent quantum yield of acceptor/TTBP blend films to 76%. Furthermore, since the donor PtOEP and the collector TTBP are separately isolated in the nanofibrous acceptor crystals, the singlet back energy transfer from the collector to the donor is effectively avoided. Such efficient singlet energy collection and inhibited back energy transfer processes result in a large increase of UC efficiency up to 9

REDUCTION OF ACIDITY OF NITRIC ACID SOLUTIONS BY USE OF FORMALDEHYDE

DOEpatents

Healy, T.V.

1958-05-20

A continuous method is described of concentrating by evaporation and reducing the nitrate ion content of an aqueous solution of metallic salts containing nitric acid not in excess of 8N. It consists of heating the solution and then passing formaldehyde into the heated solution to bring about decomposition of the nitric acid. The evolved gases containing NO are contacted countercurrently with an aqueous metal salt solution containing nitric acid in excess of 8N so as to bring about decomposition of the nitric acid and lower the normality to at least 8N, whereupon it is passed into the body of heated solution.

Solution-Phase Conformation and Dynamics of Conjugated Isoindigo-Based Donor–Acceptor Polymer Single Chains

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lee, Franklin L.; Farimani, Amir Barati; Gu, Kevin L.

Conjugated polymers are the key material in thin-film organic optoelectronic devices due to the versatility of these molecules combined with their semiconducting properties. A molecular-scale understanding of conjugated polymers is important to the optimization of the thin-film morphology. We examine the solution-phase behavior of conjugated isoindigo-based donor–acceptor polymer single chains of various chain lengths using atomistic molecular dynamics simulations. Our simulations elucidate the transition from a rod-like to a coil-like conformation from an analysis of normal modes and persistence length. In addition, we find another transition based on the solvent environment, contrasting the coil-like conformation in a good solvent withmore » a globule-like conformation in a poor solvent. Altogether, our results provide valuable insights into the transition between conformational regimes for conjugated polymers as a function of both the chain length and the solvent environment, which will help to accurately parametrize higher level models.« less

Solution-Phase Conformation and Dynamics of Conjugated Isoindigo-Based Donor–Acceptor Polymer Single Chains

DOE PAGES

Lee, Franklin L.; Farimani, Amir Barati; Gu, Kevin L.; ...

2017-10-25

Conjugated polymers are the key material in thin-film organic optoelectronic devices due to the versatility of these molecules combined with their semiconducting properties. A molecular-scale understanding of conjugated polymers is important to the optimization of the thin-film morphology. We examine the solution-phase behavior of conjugated isoindigo-based donor–acceptor polymer single chains of various chain lengths using atomistic molecular dynamics simulations. Our simulations elucidate the transition from a rod-like to a coil-like conformation from an analysis of normal modes and persistence length. In addition, we find another transition based on the solvent environment, contrasting the coil-like conformation in a good solvent withmore » a globule-like conformation in a poor solvent. Altogether, our results provide valuable insights into the transition between conformational regimes for conjugated polymers as a function of both the chain length and the solvent environment, which will help to accurately parametrize higher level models.« less

ELECTROLYTIC REDUCTION OF NITRIC ACID SOLUTIONS

DOEpatents

Alter, H.W.; Barney, D.L.

1958-09-30

A process is presented for the treatment of radioactivc waste nitric acid solutions. The nitric acid solution is neutralized with an alkali metal hydroxide in an amount sufficient to precipitate insoluble hydroxides, and after separation of the precipitate the solution is electrolyzed to convert the alkali nitrate formed, to alkali hydroxide, gaseous ammonla and oxygen. The solution is then reusable after reducing the volume by evaporating the water and dissolved ammonia.

A Nonfullerene Small Molecule Acceptor with 3D Interlocking Geometry Enabling Efficient Organic Solar Cells.

PubMed

Lee, Jaewon; Singh, Ranbir; Sin, Dong Hun; Kim, Heung Gyu; Song, Kyu Chan; Cho, Kilwon

2016-01-06

A new 3D nonfullerene small-molecule acceptor is reported. The 3D interlocking geometry of the small-molecule acceptor enables uniform molecular conformation and strong intermolecular connectivity, facilitating favorable nanoscale phase separation and electron charge transfer. By employing both a novel polymer donor and a nonfullerene small-molecule acceptor in the solution-processed organic solar cells, a high-power conversion efficiency of close to 6% is demonstrated. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Interaction of Humic Acids with Organic Toxicants

NASA Astrophysics Data System (ADS)

Tchaikovskaya, O. N.; Yudina, N. V.; Maltseva, E. V.; Nechaev, L. V.; Svetlichnyi, V. A.

2016-08-01

Interaction of humic acids with polyaromatic hydrocarbons (PAH) (naphthalene and anthracene) and triazole series fungicides (cyproconazole (CC) and tebuconazole (TC)) is investigated by the method of fluorescence quenching depending on the concentration of substances in solutions and their structural features. Humic acids were modified by mechanochemical activation in a planetary mill. The complex character of intermolecular interactions between PAH and fungicides with humic acids, including donor-acceptor and hydrophobic binding, is established. Thermodynamically stable conformations of biocide molecules were estimated using ChemOffice CS Chem3D 8.0 by methods of molecular mechanics (MM2) and molecular dynamics. Biocide molecules with pH 7 are in energetically favorable position when the benzene and triazole rings are almost parallel to each other. After acidification of solutions to pH 4.5, the CC molecule retains the geometry for which donor-acceptor interactions are possible: the benzene ring in the molecule represents the electron donor, and triazole is the acceptor. In this case, the electron density in CC is redistributed easier, which is explained by a smaller number of carbon atoms between the triazole and benzene rings, unlike TC. As a result, the TC triazole ring is protonated to a greater degree, acquiring a positive charge, and enters into donoracceptor interactions with humic acid (HA) samples. The above-indicated bond types allow HA to participate actively in sorption processes and to provide their interaction with biocides and PAH and hence, to act as detoxifying agents for recultivation of the polluted environment.

Lewis acid catalyzed [3 + 2] annulation of ketenimines with donor-acceptor cyclopropanes: an approach to 2-alkylidenepyrrolidine derivatives.

PubMed

Alajarin, Mateo; Egea, Adrian; Orenes, Raul-Angel; Vidal, Angel

2016-11-02

The [3 + 2] annulation reaction of C,C,N-trisubstituted ketenimines with donor-acceptor cyclopropanes bearing aryl, styryl and vinyl substituents at the C2 position, triggered by the Lewis acid Sc(OTf) 3 , supplies highly substituted pyrrolidines. Activated cyclopropanes fused to naphthalene and [1]benzopyrane nuclei are also suitable substrates in similar transformations, yielding partially saturated benz[g]indoles and [1]benzopyran[4,3-b]pyrroles. An intramolecular version of this ketenimine/cyclopropane [3 + 2] annulation has also been developed leading to the pyrrolo[2,1-a]isoindole framework.

Spectrophotometric and spectroscopic studies of charge transfer complex of 1-Naphthylamine as an electron donor with picric acid as an electron acceptor in different polar solvents

NASA Astrophysics Data System (ADS)

Singh, Neeti; Ahmad, Afaq

2010-08-01

The charge transfer complex of 1-Naphthylamine as a donor with π-acceptor picric acid has been studied spectrophotometrically in different solvents at room temperature. The results indicate that the formation of charge transfer complex is high in less polar solvent. The stoichiometry of the complex was found to be 1:1 by straight line method. The data are analysed in terms of formation constant ( KCT), molar extinction coefficient ( ɛCT), standard free energy (Δ G o), oscillator strength ( ƒ), transition dipole moment ( μ EN), resonance energy ( R N) and ionization potential ( I D). It is concluded that the formation constant ( KCT) of the complex is found to be depends upon the nature of both electron acceptor and donor and also on the polarity of solvents. Further the charge transfer molecular complex between picric acid and 1-Naphthylamine is stabilized by hydrogen bonding.

Synthesis and electrochemical studies of charge-transfer complexes of thiazolidine-2,4-dione with σ and π acceptors

NASA Astrophysics Data System (ADS)

Singh, Prashant; Kumar, Pradeep; Katyal, Anju; Kalra, Rashmi; Dass, Sujata K.; Prakash, Satya; Chandra, Ramesh

2010-03-01

In the present work, we report the synthesis and characterization of novel charge-transfer complexes of thiazolidine-2,4-dione (TZD) with sigma acceptor (iodine) and pi acceptors (chloranil, dichlorodicyanoquinone, picric acid and duraquinone). We also evaluated their thermal and electrochemical properties and we conclude that these complexes are frequency dependent. Charge-transfer complex between thiazolidine-2,4-dione and iodine give best conductivity. In conclusion, complex with sigma acceptors are more conducting than with pi acceptors.

A Simple Procedure for Constructing 5'-Amino-Terminated Oligodeoxynucleotides in Aqueous Solution

NASA Technical Reports Server (NTRS)

Bruick, Richard K.; Koppitz, Marcus; Joyce, Gerald F.; Orgel, Leslie E.

1997-01-01

A rapid method for the synthesis of oligodeoxynucleotides (ODNs) terminated by 5'-amino-5'-deoxythymidine is described. A 3'-phosphorylated ODN (the donor) is incubated in aqueous solution with 5'-amino- 5'-deoxythymidine in the presence of N-(3-dimethylaminopropyl)-)N'-ethylcarbodiimide hydrochloride (EDC), extending the donor by one residue via a phosphoramidate bond. Template- directed ligation of the extended donor and an acceptor ODN, followed by acid hydrolysis, yields the acceptor ODN extended by a single 5'-amino-5'-deoxythymidine residue at its 5'terminus.

Shedding light on the photostability of two intermolecular charge-transfer complexes between highly fluorescent bis-1,8-naphthalimide dyes and some π-acceptors: A spectroscopic study in solution and solid states

NASA Astrophysics Data System (ADS)

Refat, Moamen S.; Ismail, Lamia A.; Adam, Abdel Majid A.

2015-01-01

Given the great importance of the various uses of 1,8-naphthalimides in the trends of biology, medicine and industry, the current study focused on extending the scope of these dyes by introducing some of their charge-transfer (CT) complexes. For this purpose, two highly fluorescent bis-1,8-naphthalimide dyes and their complexes with some π-acceptors have been synthesized and characterized spectroscopically. The π-acceptors include picric acid (PA), chloranilic acid (CLA), tetracyanoquinodimethane (TCNQ) and dichlorodicyanobenzoquinone (DDQ). The molecular structure, spectroscopic and fluorescence properties as well as the binding modes were deduced from IR, UV-vis and 1H NMR spectral studies. The binding ratio of complexation was determined to be 1:1 according to the elemental analyses and photometric titrations. It has been found that the order of acceptance ability for the different acceptors is TCNQ > DDQ > CLA > PA. The photostability of 1,8-naphthalimide dye as a donor and its charge-transfer complex doped in polymethyl methacrylate/PMMA were exposed to UV-Vis radiation and the change in the absorption spectra was achieved at different times during irradiation period.

Spectroscopic and thermal investigations of charge-transfer complexes formed between sulfadoxine drug and different types of acceptors

NASA Astrophysics Data System (ADS)

Refat, Moamen S.

2011-01-01

Charge-transfer reactions between sulfadoxine (SDOX) as a donor with iodine (I 2), 2,3-dichloro-5,6-dicyano-1,4-benzoquinone (DDQ), p-chloranil (CHL) and picric acid (PA) have been studied in solid and solution forms. The stoichiometry of all complexes was found to be 1:1 by molar ratio method between donor and acceptor at a CT-band absorption bands. The data are discussed in terms of formation constant ( KCT), molar extinction coefficient ( ɛCT), standard free energy (Δ Go), oscillator strength (ƒ), transition dipole moment ( μ), resonance energy ( RN) and ionization potential ( ID). The results indicate that the formation constant ( KCT) for the complexes were shown to be dependent upon the nature of electron acceptor, donor and polarity of solvents which were used. IR, 1H NMR and UV-Vis spectroscopic techniques, Elemental analyses (CHN) and TG-DTG investigation were used to characterize the four sulfadoxine charge-transfer complexes.

Decomposition mechanism of chromite in sulfuric acid-dichromic acid solution

NASA Astrophysics Data System (ADS)

Zhao, Qing; Liu, Cheng-jun; Li, Bao-kuan; Jiang, Mao-fa

2017-12-01

The sulfuric acid leaching process is regarded as a promising, cleaner method to prepare trivalent chromium products from chromite; however, the decomposition mechanism of the ore is poorly understood. In this work, binary spinels of Mg-Al, Mg-Fe, and Mg-Cr in the powdered and lump states were synthesized and used as raw materials to investigate the decomposition mechanism of chromite in sulfuric acid-dichromic acid solution. The leaching yields of metallic elements and the changes in morphology of the spinel were studied. The experimental results showed that the three spinels were stable in sulfuric acid solution and that dichromic acid had little influence on the decomposition behavior of the Mg-Al spinel and Mg-Fe spinel because Mg2+, Al3+, and Fe3+ in spinels cannot be oxidized by Cr6+. However, in the case of the Mg-Cr spinel, dichromic acid substantially promoted the decomposition efficiency and functioned as a catalyst. The decomposition mechanism of chromite in sulfuric acid-dichromic acid solution was illustrated on the basis of the findings of this study.

Spectrophotometric and spectroscopic studies of charge transfer complexes of p-toluidine as an electron donor with picric acid as an electron acceptor in different solvents.

PubMed

Singh, Neeti; Khan, Ishaat M; Ahmad, Afaq

2010-04-01

The charge transfer complexes of the donor p-toluidine with pi-acceptor picric acid have been studied spectrophotometrically in various solvents such as carbon tetrachloride, chloroform, dichloromethane acetone, ethanol, and methanol at room temperature using absorption spectrophotometer. The results indicate that formation of CTC in non-polar solvent is high. The stoichiometry of the complex was found to be 1:1 ratio by straight-line method between donor and acceptor with maximum absorption bands. The data are discussed in terms of formation constant (K(CT)), molar extinction coefficient (epsilon(CT)), standard free energy (DeltaG(o)), oscillator strength (f), transition dipole moment (mu(EN)), resonance energy (R(N)) and ionization potential (I(D)). The results indicate that the formation constant (K(CT)) for the complex was shown to be dependent upon the nature of electron acceptor, donor and polarity of solvents that were used. Copyright 2010 Elsevier B.V. All rights reserved.

Nitric acid recovery from waste solutions

DOEpatents

Wilson, A. S.

1959-04-14

The recovery of nitric acid from aqueous nitrate solutions containing fission products as impurities is described. It is desirable to subject such solutions to concentration by evaporation since nitric acid is regenerated thereby. A difficulty, however, is that the highly radioactive fission product ruthenium is volatilized together with the nitric acid. It has been found that by adding nitrous acid, ruthenium volatilization is suppressed and reduced to a negligible degree so that the distillate obtained is practically free of ruthenium.

Solubility limits of dibutyl phosphoric acid in uranium-nitric acid solutions

DOE Office of Scientific and Technical Information (OSTI.GOV)

Pierce, R.A.

2000-01-04

The Savannah River Site has enriched uranium (EU) solution that has been stored since being purified in its solvent extraction processes. The concentrations in solution are approximately 6 g/L U and 0.1 M nitric acid. Residual tributylphosphate in solution has slowly hydrolyzed to form dibutyl phosphoric acid (HDBP) at concentrations averaging 30--50 mg/L. Dibutyl phosphoric acid, in turn, is in equilibrium with (HDBP){sub 2} and DBP{sup {minus}}. Uranium can form compounds with the dibutylphosphate ion (DBP{sup {minus}}) which have limited solubility, thereby creating a nuclear criticality safety issue. Literature reports and earlier SRTC tests have shown that it is feasiblemore » to precipitate U-DBP solid during the storage and processing of EU solutions. As a result, a series of solubility experiments were run at nitric acid concentrations from 0--4.0 M HNO{sub 3}, uranium at 0--90 g/L, and temperatures from 0--30 C. The data shows temperature and nitric acid concentration dependence consistent with what would be expected. With respect to uranium concentration, U-DBP solubility passes through a minimum between 6 and 12 g/L U at the acid concentrations and temperatures studied. However, the minimum shows a slight shift toward lower uranium concentrations at lower nitric acid concentrations. The shifts in solubility are strongly dependent upon the overall ionic strength of the solution. The data also reveal a shift to higher DBP solubility above 0.5 M HNO{sub 3} for both 6 g/L and 12 g/L uranium solutions. Analysis of U-DBP solids from the tests identified distinct differences between precipitates from less than 0.5 M solutions and those from greater than 4 M acid. Analyses identified UO{sub 2}(DBP){sub 2} as the dominant compound present at low acid concentrations in accordance with literature reports. As the acid concentration increases, the crystalline UO{sub 2}(DBP){sub 2} shows molecular substitutions and an increase in amorphous content.« less

Anaerobic methanotrophy in tidal wetland: Effects of electron acceptors

NASA Astrophysics Data System (ADS)

Lin, Li-Hung; Yu, Zih-Huei; Wang, Pei-Ling

2016-04-01

Wetlands have been considered to represent the largest natural source of methane emission, contributing substantially to intensify greenhouse effect. Despite in situ methanogenesis fueled by organic degradation, methanotrophy also plays a vital role in controlling the exact quantity of methane release across the air-sediment interface. As wetlands constantly experience various disturbances of anthropogenic activities, biological burrowing, tidal inundation, and plant development, rapid elemental turnover would enable various electron acceptors available for anaerobic methanotrophy. The effects of electron acceptors on stimulating anaerobic methanotrophy and the population compositions involved in carbon transformation in wetland sediments are poorly explored. In this study, sediments recovered from tidally influenced, mangrove covered wetland in northern Taiwan were incubated under the static conditions to investigate whether anaerobic methanotrophy could be stimulated by the presence of individual electron acceptors. Our results demonstrated that anaerobic methanotrophy was clearly stimulated in incubations amended with no electron acceptor, sulfate, or Fe-oxyhydroxide. No apparent methane consumption was observed in incubations with nitrate, citrate, fumarate or Mn-oxides. Anaerobic methanotrophy in incubations with no exogenous electron acceptor appears to proceed at the greatest rates, being sequentially followed by incubations with sulfate and Fe-oxyhydroxide. The presence of basal salt solution stimulated methane oxidation by a factor of 2 to 3. In addition to the direct impact of electron acceptor and basal salts, incubations with sediments retrieved from low tide period yielded a lower rate of methane oxidation than from high tide period. Overall, this study demonstrates that anaerobic methanotrophy in wetland sediments could proceed under various treatments of electron acceptors. Low sulfate content is not a critical factor in inhibiting methane

Associative Memory Acceptors.

ERIC Educational Resources Information Center

Card, Roger

The properties of an associative memory are examined in this paper from the viewpoint of automata theory. A device called an associative memory acceptor is studied under real-time operation. The family "L" of languages accepted by real-time associative memory acceptors is shown to properly contain the family of languages accepted by one-tape,…

Demonstration of FRET in solutions

NASA Astrophysics Data System (ADS)

Shah, Sunil; Gryczynski, Zygmunt; Chib, Rahul; Fudala, Rafal; Baxi, Aatmun; Borejdo, Julian; Synak, Anna; Gryczynski, Ignacy

2016-03-01

We measured the Förster resonance energy transfer (FRET) from Uranin (U) donor to Rhodamine 101 (R101) acceptor in propylene glycol. Steady-state fluorescence measurements show a significant difference between mixed and unmixed fluorophore solutions. In the solution with mixed fluorophores, fluorescence intensity of the U donor decreases and intensity of R101 fluorescence increases. This is visualized as a color change from green to orange. Fluorescence anisotropy of the mixture solution increases in the donor emission wavelength region and decreases in the acceptor emission wavelengths; which is consistent with FRET occurrence. Time-resolved (lifetime) measurements show a decrease of the U lifetime in the presence of R101 acceptor. In the intensity decay of R101 acceptor appears a negative component indicating excited state process. All these measurements prove the presence of FRET in U/R101 mixture fluorescence.

Enhanced nonlinear optical responses in donor-acceptor ionic complexes via photo induced energy transfer.

PubMed

Mamidala, Venkatesh; Polavarapu, Lakshminarayana; Balapanuru, Janardhan; Loh, Kian Ping; Xu, Qing-Hua; Ji, Wei

2010-12-06

By complexion of donor and acceptor using ionic interactions, the enhanced nonlinear optical responses of donor-acceptor ionic complexes in aqueous solution were studied with 7-ns laser pulses at 532 nm. The optical limiting performance of negatively charged gold nanoparticles or graphene oxide (Acceptor) was shown to be improved significantly when they were mixed with water-soluble, positively-charged porphyrin (Donor) derivative. In contrast, no enhancement was observed when mixing with negatively-charged porphyrin. Transient absorption studies of the donor-acceptor complexes confirmed that the addition of energy transfer pathway were responsible for excited-state deactivation, which results in the observed enhancement. Fluence, angle-dependent scattering and time correlated single photon counting measurements suggested that the enhanced nonlinear scattering due to faster nonradiative decay should play a major role in the enhanced optical limiting responses.

Acceptor and Excitation Density Dependence of the Ultrafast Polaron Absorption Signal in Donor-Acceptor Organic Solar Cell Blends.

PubMed

Zarrabi, Nasim; Burn, Paul L; Meredith, Paul; Shaw, Paul E

2016-07-21

Transient absorption spectroscopy on organic semiconductor blends for solar cells typically shows efficient charge generation within ∼100 fs, accounting for the majority of the charge carriers. In this Letter, we show using transient absorption spectroscopy on blends containing a broad range of acceptor content (0.01-50% by weight) that the rise of the polaron signal is dependent on the acceptor concentration. For low acceptor content (<10% by weight), the polaron signal rises gradually over ∼1 ps with most polarons generated after 200 fs, while for higher acceptor concentrations (>10%) most polarons are generated within 200 fs. The rise time in blends with low acceptor content was also found to be sensitive to the pump fluence, decreasing with increasing excitation density. These results indicate that the sub-100 fs rise of the polaron signal is a natural consequence of both the high acceptor concentrations in many donor-acceptor blends and the high excitation densities needed for transient absorption spectroscopy, which results in a short average distance between the exciton and the donor-acceptor interface.

Nitric acid uptake by sulfuric acid solutions under stratospheric conditions - Determination of Henry's Law solubility

NASA Technical Reports Server (NTRS)

Reihs, Christa M.; Golden, David M.; Tolbert, Margaret A.

1990-01-01

The uptake of nitric acid by sulfuric acid solutions representative of stratospheric particulate at low temperatures was measured to determine the solubility of nitric acid in sulfuric acid solutions as a function of H2SO4 concentration and solution temperature. Solubilities are reported for sulfuric acid solutions ranging from 58 to 87 wt pct H2SO4 over a temperature range from 188 to 240 K, showing that, in general, the solubility of nitric acid increases with decreasing sulfuric acid concentration and with decreasing temperature. The measured solubilities indicate that nitric acid in the global stratosphere will be found predominantly in the gas phase.

Methods for the synthesis of donor-acceptor cyclopropanes

NASA Astrophysics Data System (ADS)

Tomilov, Yu V.; Menchikov, L. G.; Novikov, R. A.; Ivanova, O. A.; Trushkov, I. V.

2018-03-01

The interest in cyclopropane derivatives is caused by the facts that, first, the three-carbon ring is present in quite a few natural and biologically active compounds and, second, compounds with this ring are convenient building blocks for the synthesis of diverse molecules (acyclic, alicyclic and heterocyclic). The carbon–carbon bonds in cyclopropane are kinetically rather inert; hence, they need to be activated to be involved in reactions. An efficient way of activation is to introduce vicinal electron-donating and electron-withdrawing substituents into the ring; these substrates are usually referred to as donor-acceptor cyclopropanes. This review gives a systematic account of the key methods for the synthesis of donor-acceptor cyclopropanes. The most important among them are reactions of nucleophilic alkenes with diazo compounds and iodonium ylides and approaches based on reactions of electrophilic alkenes with sulfur ylides (the Corey–Chaykovsky reaction). Among other methods used for this purpose, noteworthy are cycloalkylation of CH-acids, addition of α-halocarbonyl compounds to alkenes, cyclization via 1,3-elimination, reactions of alkenes with halocarbenes followed by reduction, the Simmons–Smith reaction and some other. The scope of applicability and prospects of various methods for the synthesis of donor-acceptor cyclopropanes are discussed. The bibliography includes 530 references.

Acceptors in ZnO

DOE PAGES

Mccluskey, Matthew D.; Corolewski, Caleb; Lv, Jinpeng; ...

2015-03-21

Zinc oxide (ZnO) has potential for a range of applications in the area of optoelectronics. The quest for p-type ZnO has focused much attention on acceptors. In this paper, Cu, N, and Li acceptor impurities are discussed. Experimental evidence shows that these point defects have acceptor levels 3.2, 1.5, and 0.8 eV above the valence-band maximum, respectively. The levels are deep because the ZnO valence band is quite low compared to conventional, non-oxide semiconductors. Using MoO2 contacts, the electrical resistivity of ZnO:Li was measured and showed behavior consistent with bulk hole conduction for temperatures above 400 K. A photoluminescence peakmore » in ZnO nanocrystals has been attributed to an acceptor, which may involve a zinc vacancy. High field (W-band) electron paramagnetic resonance measurements on the nanocrystals revealed an axial center with g = 2.0033 and g = 2.0075, along with an isotropic center at g = 2.0053.« less

Donor assists acceptor binding and catalysis of human α1,6-fucosyltransferase.

PubMed

Kötzler, Miriam P; Blank, Simon; Bantleon, Frank I; Wienke, Martin; Spillner, Edzard; Meyer, Bernd

2013-08-16

α1,6-Core-fucosyltransferase (FUT8) is a vital enzyme in mammalian physiological and pathophysiological processes such as tumorigenesis and progress of, among others, non-small cell lung cancer and colon carcinoma. It was also shown that therapeutic antibodies have a dramatically higher efficacy if the α1,6-fucosyl residue is absent. However, specific and potent inhibitors for FUT8 and related enzymes are lacking. Hence, it is crucial to elucidate the structural basis of acceptor binding and the catalytic mechanism. We present here the first structural model of FUT8 in complex with its acceptor and donor molecules. An unusually large acceptor, i.e., a hexasaccharide from the core of N-glycans, is required as minimal structure. Acceptor substrate binding of FUT8 is being dissected experimentally by STD NMR and SPR and theoretically by molecular dynamics simulations. The acceptor binding site forms an unusually large and shallow binding site. Binding of the acceptor to the enzyme is much faster and stronger if the donor is present. This is due to strong hydrogen bonding between O6 of the proximal N-acetylglucosamine and an oxygen atom of the β-phosphate of GDP-fucose. Therefore, we propose an ordered Bi Bi mechanism for FUT8 where the donor molecule binds first. No specific amino acid is present that could act as base during catalysis. Our results indicate a donor-assisted mechanism, where an oxygen of the β-phosphate deprotonates the acceptor. Knowledge of the mechanism of FUT8 is now being used for rational design of targeted inhibitors to address metastasis and prognosis of carcinomas.

Comparative phytotoxicity of usnic acid, salicylic acid, cinnamic acid and benzoic acid on photosynthetic apparatus of Chlamydomonas reinhardtii.

PubMed

Gao, Yazhi; Liu, Wei; Wang, Xiaoxiong; Yang, Lihua; Han, Su; Chen, Shiguo; Strasser, Reto Jörg; Valverde, Bernal E; Qiang, Sheng

2018-07-01

The effects of four phytotoxins usnic acid (UA), salicylic acid (SA), cinnamic acid (CA) and benzoic acid (BA) on photosynthesis of Chlamydomonas reinhardtii were studied in vivo to identify and localise their initial action sites on two photosystems. Our experimental evidence shows that the four phytotoxins have multiple targets in chloroplasts, which mainly lie in photosystem II (PSII), not photosystem I (PSI). They share an original action site by blocking electron transport beyond Q A (primary plastoquinone acceptor) at PSII acceptor side since a fast increase of the J-step level is the greatest change in chlorophyll a fluorescence induction kinetics OJIP in C. reinhardtii cells treated with the phytotoxins. UA decreases photosynthetic activity by reducing O 2 evolution rate, interrupting PSII electron transport at both the donor and acceptor sides, inactivating the PSII reaction centers (RCs), reducing the content of chlorophylls and carotenoids, destroying the conformation of antenna pigment assemblies, and casuing the degradation of D1/D2 proteins. SA damage to photosynthetic machinery is mainly attributed to inhibition of PSII electron transport beyond Q A at the acceptor side, inactivation of the PSII RCs, reduction of chlorophyll content, digestion of thylakoid ploypeptides and destabilization of thylakoid membranes. Both CA and BA affect the photosynthetic process by decreasing PSII electron transport efficiency at the acceptor side and the amount of active PSII RCs. Besides, the initial cause of BA-inhibiting photosynthesis is also assocaited with the O 2 evolution rate and the disconnection of some antenna molecules from PSII RCs. Copyright © 2018 Elsevier Masson SAS. All rights reserved.

Reference electrode for strong oxidizing acid solutions

DOEpatents

Rigdon, Lester P.; Harrar, Jackson E.; Bullock, Sr., Jack C.; McGuire, Raymond R.

1990-01-01

A reference electrode for the measurement of the oxidation-reduction potentials of solutions is especially suitable for oxidizing solutions such as highly concentrated and fuming nitric acids, the solutions of nitrogen oxides, N.sub.2 O.sub.4 and N.sub.2 O.sub.5, in nitric acids. The reference electrode is fabricated of entirely inert materials, has a half cell of Pt/Ce(IV)/Ce(III)/70 wt. % HNO.sub.3, and includes a double-junction design with an intermediate solution of 70 wt. % HNO.sub.3. The liquid junctions are made from Corning No. 7930 glass for low resistance and negligible solution leakage.

A paper-based resonance energy transfer nucleic acid hybridization assay using upconversion nanoparticles as donors and quantum dots as acceptors.

PubMed

Doughan, Samer; Uddayasankar, Uvaraj; Krull, Ulrich J

2015-06-09

Monodisperse aqueous upconverting nanoparticles (UCNPs) were covalently immobilized on aldehyde modified cellulose paper via reduction amination to develop a luminescence resonance energy transfer (LRET)-based nucleic acid hybridization assay. This first account of covalent immobilization of UCNPs on paper for a bioassay reports an optically responsive method that is sensitive, reproducible and robust. The immobilized UCNPs were decorated with oligonucleotide probes to capture HPRT1 housekeeping gene fragments, which in turn brought reporter conjugated quantum dots (QDs) in close proximity to the UCNPs for LRET. This sandwich assay could detect unlabeled oligonucleotide target, and had a limit of detection of 13 fmol and a dynamic range spanning nearly 3 orders of magnitude. The use of QDs, which are excellent LRET acceptors, demonstrated improved sensitivity, limit of detection, dynamic range and selectivity compared to similar assays that have used molecular fluorophores as acceptors. The selectivity of the assay was attributed to the decoration of the QDs with polyethylene glycol to eliminate non-specific adsorption. The kinetics of hybridization were determined to be diffusion limited and full signal development occurred within 3 min. Copyright © 2015 Elsevier B.V. All rights reserved.

Acceptor Ionization Energies in GaN*

NASA Astrophysics Data System (ADS)

Wang, Hao; Ban Chen, An

2001-03-01

The k.p Hamiltonian and a model potential are used to deduce the acceptor ionization energies in GaN from a systematic study of the chemical trend in GaAs, GaP, and InP. The acceptors studied include Be, Mg, Ca, Zn, and Cd on the cation sites and C, Si, and Ge on the anion sites. Our calculated acceptor ionization energies are estimated to be accurate to better than ten percent across the board. The ionization energies of C and Be (152 and 187 meV respectively) in wurtzite GaN are found to be lower than that of Mg (224 meV). The C was found to behave like the hydrogenic acceptor in all systems and it has the smallest ionization energy among all the acceptors studied.

(3+3)-Annulation of Donor-Acceptor Cyclopropanes with Diaziridines.

PubMed

Trushkov, Igor V; Chagarovskiy, Alexey O; Vasin, Vladimir S; Kuznetsov, Vladimir V; Ivanova, Olga A; Rybakov, Victor B; Shumsky, Alexey N; Makhova, Nina N

2018-06-23

The first example of (3+3)-annulation of two different three-membered rings is reported herein. Donor-acceptor cyclopropanes in reaction with diaziridines were found to afford perhydropyridazine derivatives in high yields and diastereoselectivity under mild Lewis acid catalysis. The disclosed reaction is applicable for the broad substrate scope and exhibits an excellent functional group tolerance. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Process for the extraction of strontium from acidic solutions

DOEpatents

Horwitz, E. Philip; Dietz, Mark L.

1994-01-01

The invention is a process for selectively extracting strontium values from aqueous nitric acid waste solutions containing these and other fission product values. The extractant solution is a macrocyclic polyether in an aliphatic hydrocarbon diluent containing a phase modifier. The process will selectively extract strontium values from nitric acid solutions which are up to 6 molar in nitric acid.

Process for the extraction of strontium from acidic solutions

DOEpatents

Horwitz, E.P.; Dietz, M.L.

1993-01-01

The invention is a process for selectively extracting strontium values from aqueous nitric acid waste solutions containing these and other fission product values. The extractant solution is a macrocyclic polyether in an aliphatic hydrocarbon diluent containing a phase modifier. The process will selectively extract strontium values from nitric acid solutions which are up to 6 molar in nitric acid.

Proton transfer complexes based on some π-acceptors having acidic protons with 3-amino-6-[2-(2-thienyl)vinyl]-1,2,4-triazin-5(4 H)-one donor: Synthesis and spectroscopic characterizations

NASA Astrophysics Data System (ADS)

Refat, Moamen S.; Saad, Hosam A.; Adam, Abdel Majid A.

2011-05-01

Charge transfer complexes based on 3-amino-6-[2-(2-thienyl)vinyl]-1,2,4-triazin-5(4 H)-one (ArNH 2) organic basic donor and pi-acceptors having acidic protons such as picric acid (PiA), hydroquinone (Q(OH) 2) and 3,5-dinitrobenzene (DNB) have been synthesized and spectroscopically studied. The sbnd NH3+ ammonium ion was formed under the acid-base theory through proton transfer from an acidic to basic centers in all charge transfer complexes resulted. The values of formation constant ( KCT) and molar extinction coefficient ( ɛCT) which were estimated from the spectrophotometric studies have a dramatic effect for the charge transfer complexes with differentiation of pi-acceptors. For further studies the vibrational spectroscopy of the [( ArNH3+)(PiA -)] (1), [( ArNH3+)(Q (OH)2-)] (2) and [( ArNH3+)(DNB -)] (3) of (1:1) charge transfer complexes of (donor: acceptor) were characterized by elemental analysis, infrared spectra, Raman spectra, 1H and 13CNMR spectra. The experimental data of elemental analyses of the charge transfer complexes (1), (2) and (3) were in agreement with calculated data. The IR and Raman spectra of (1), (2) and (3) are indicated to the presence of bands around 3100 and 1600 cm -1 distinguish to sbnd NH3+. The thermogravimetric analysis (TG) and differential scanning calorimetry (DSC) techniques were performed to give knowledge about thermal stability behavior of the synthesized charge transfer complexes. The morphological features of start materials and charge transfer complexes were investigated using scanning electron microscopy (SEM) and optical microscopy.

Process for the extraction of strontium from acidic solutions

DOEpatents

Horwitz, E.P.; Dietz, M.L.

1994-09-06

The invention is a process for selectively extracting strontium values from aqueous nitric acid waste solutions containing these and other fission product values. The extractant solution is a macrocyclic polyether in an aliphatic hydrocarbon diluent containing a phase modifier. The process will selectively extract strontium values from nitric acid solutions which are up to 6 molar in nitric acid. 4 figs.

Non-Fullerene Electron Acceptors for Use in Organic Solar Cells

PubMed Central

2015-01-01

Conspectus The active layer in a solution processed organic photovoltaic device comprises a light absorbing electron donor semiconductor, typically a polymer, and an electron accepting fullerene acceptor. Although there has been huge effort targeted to optimize the absorbing, energetic, and transport properties of the donor material, fullerenes remain as the exclusive electron acceptor in all high performance devices. Very recently, some new non-fullerene acceptors have been demonstrated to outperform fullerenes in comparative devices. This Account describes this progress, discussing molecular design considerations and the structure–property relationships that are emerging. The motivation to replace fullerene acceptors stems from their synthetic inflexibility, leading to constraints in manipulating frontier energy levels, as well as poor absorption in the solar spectrum range, and an inherent tendency to undergo postfabrication crystallization, resulting in device instability. New acceptors have to address these limitations, providing tunable absorption with high extinction coefficients, thus contributing to device photocurrent. The ability to vary and optimize the lowest unoccupied molecular orbital (LUMO) energy level for a specific donor polymer is also an important requirement, ensuring minimal energy loss on electron transfer and as high an internal voltage as possible. Initially perylene diimide acceptors were evaluated as promising acceptor materials. These electron deficient aromatic molecules can exhibit good electron transport, facilitated by close packed herringbone crystal motifs, and their energy levels can be synthetically tuned. The principal drawback of this class of materials, their tendency to crystallize on too large a length scale for an optimal heterojunction nanostructure, has been shown to be overcome through introduction of conformation twisting through steric effects. This has been primarily achieved by coupling two units together

Solution-phase electronegativity scale: insight into the chemical behaviors of metal ions in solution.

PubMed

Li, Keyan; Li, Min; Xue, Dongfeng

2012-04-26

By incorporating the solvent effect into the Born effective radius, we have proposed an electronegativity scale of metal ions in aqueous solution with the most common oxidation states and hydration coordination numbers in terms of the effective ionic electrostatic potential. It is found that the metal ions in aqueous solution are poorer electron acceptors compared to those in the gas phase. This solution-phase electronegativity scale shows its efficiency in predicting some important properties of metal ions in aqueous solution such as the aqueous acidities of the metal ions, the stability constants of metal complexes, and the solubility product constants of the metal hydroxides. We have elaborated that the standard reduction potential and the solution-phase electronegativity are two different quantities for describing the processes of metal ions in aqueous solution to soak up electrons with different final states. This work provides a new insight into the chemical behaviors of the metal ions in aqueous solution, indicating a potential application of this electronegativity scale to the design of solution reactions.

Raman spectra of amino acids and their aqueous solutions

NASA Astrophysics Data System (ADS)

Zhu, Guangyong; Zhu, Xian; Fan, Qi; Wan, Xueliang

2011-03-01

Amino acids are the basic "building blocks" that combine to form proteins and play an important physiological role in all life-forms. Amino acids can be used as models for the examination of the importance of intermolecular bonding in life processes. Raman spectra serve to obtain information regarding molecular conformation, giving valuable insights into the topology of more complex molecules (peptides and proteins). In this paper, amino acids and their aqueous solution have been studied by Raman spectroscopy. Comparisons of certain values for these frequencies in amino acids and their aqueous solutions are given. Spectra of solids when compared to those of the solute in solution are invariably much more complex and almost always sharper. We present a collection of Raman spectra of 18 kinds of amino acids ( L-alanine, L-arginine, L-aspartic acid, cystine, L-glutamic acid, L-glycine, L-histidine, L-isoluecine, L-leucine, L-lysine, L-phenylalanine, L-methionone, L-proline, L-serine, L-threonine, L-tryptophan, L-tyrosine, L-valine) and their aqueous solutions that can serve as references for the interpretation of Raman spectra of proteins and biological materials.

Charge-transfer complexes of sulfamethoxazole drug with different classes of acceptors

NASA Astrophysics Data System (ADS)

Refat, Moamen S.; El-Korashy, Sabry A.; El-Deen, Ibrahim M.; El-Sayed, Shaima M.

2010-09-01

The charge-transfer complexes of the donor sulfamethoxazole (SZ) with iodine (I 2), 2,3-dichloro-5,6-dicyano-1,4-benzoquinone (DDQ), p-chloranil (CHL) and picric acid (PA) have been studied spectrophotometrically in chloroform or methanol at room temperature using absorption spectrophotometer. The results indicate that formation of CT-complexes in case of four acceptors. The stoichiometry of the complexes was found to be 1:1 ratio by molar ratio method between donor and acceptor with maximum absorption bands (CT band). The data are discussed in terms of formation constant ( KCT), molar extinction coefficient ( ɛCT), standard free energy (Δ G°), oscillator strength (ƒ), transition dipole moment ( μ), resonance energy ( RN) and ionization potential ( ID). The results indicate that the formation constant ( KCT) for the complexes were shown to be dependent upon the nature of electron acceptor, donor and polarity of solvents which were used. IR, 1H NMR, mass spectra, UV-Vis techniques, elemental analyses (CHN) and TG-DTG investigation were used to characterize the four sulfamethoxazole charge-transfer complexes.

Synthesis, characterization, spectrophotometric, structural and antimicrobial studies of the newly charge transfer complex of p-phenylenediamine with π acceptor picric acid

NASA Astrophysics Data System (ADS)

Khan, Ishaat M.; Ahmad, Afaq; Oves, M.

2010-12-01

Charge transfer complex (CTC) of donor, p-phenylenediamine (PPD) and acceptor, 2,4,6-trinitrophenol (picric acid) has been studied in methanol at room temperature. The CT complex was synthesized and characterized by elemental analysis, FTIR spectra, 1H NMR spectroscopy and electronic absorption spectra which indicate the CT interaction associated with proton migration from the acceptor to the donor followed by hydrogen bonding via N +-H⋯O -. The thermal stability of CT complex was studied using TGA and DTA analyses techniques. The CT complex was screened for its antifungal activity against Aspergillus niger (Laboratory isolate), Candida albicans (IQA-109) and Penicillium sp. (Laboratory isolate) and antibacterial activity against two Gram-positive bacteria Staphylococcus aureus (MSSA 22) and Bacillus subtilis (ATCC 6051) and two Gram-negative bacteria Escherichia coli (K 12) and Pseudomonas aeruginosa (MTCC 2488). It gives good antimicrobial activity. The stoichiometry of the CT complex was found to be 1:1. The physical parameters of CT complex were evaluated by the Benesi-Hildebrand equation. On the basis of the studies, the structure of CT complex is [(PPDH) +(PA) -], and a general mechanism for its formation is proposed.

Synthesis, characterization, spectrophotometric, structural and antimicrobial studies of the newly charge transfer complex of p-phenylenediamine with π acceptor picric acid.

PubMed

Khan, Ishaat M; Ahmad, Afaq; Oves, M

2010-12-01

Charge transfer complex (CTC) of donor, p-phenylenediamine (PPD) and acceptor, 2,4,6-trinitrophenol (picric acid) has been studied in methanol at room temperature. The CT complex was synthesized and characterized by elemental analysis, FTIR spectra, 1H NMR spectroscopy and electronic absorption spectra which indicate the CT interaction associated with proton migration from the acceptor to the donor followed by hydrogen bonding via N+-H⋯O-. The thermal stability of CT complex was studied using TGA and DTA analyses techniques. The CT complex was screened for its antifungal activity against Aspergillus niger (Laboratory isolate), Candida albicans (IQA-109) and Penicillium sp. (Laboratory isolate) and antibacterial activity against two Gram-positive bacteria Staphylococcus aureus (MSSA 22) and Bacillus subtilis (ATCC 6051) and two Gram-negative bacteria Escherichia coli (K 12) and Pseudomonas aeruginosa (MTCC 2488). It gives good antimicrobial activity. The stoichiometry of the CT complex was found to be 1:1. The physical parameters of CT complex were evaluated by the Benesi-Hildebrand equation. On the basis of the studies, the structure of CT complex is [(PPDH)+(PA)-], and a general mechanism for its formation is proposed. Copyright © 2010 Elsevier B.V. All rights reserved.

Fate of microbial metabolites of hydrocarbons in a coastal plain aquifer: The role of electron acceptors

USGS Publications Warehouse

Cozzarelli, I.M.; Herman, J.S.; Baedecker, M. Jo

1995-01-01

A combined field and laboratory study was undertaken to understand the distribution and geochemical conditions that influence the prevalence of low molecular weight organic acids in groundwater of a shallow aquifer contaminated with gasoline. Aromatic hydrocarbons from gasoline were degraded by microbially mediated oxidation-reduction reactions, including reduction of nitrate, sulfate, and Fe(III). The biogeochemical reactions changed overtime in response to changes in the hydrogeochemical conditions in the aquifer. Aliphatic and aromatic organic acids were associated with hydrocarbon degradation in anoxic zones of the aquifer. Laboratory microcosms demonstrated that the biogeochemical fate of specific organic acids observed in groundwater varied with the structure of the acid and the availability of electron acceptors. Benzoic and phenylacetic acid were degraded by indigenous aquifer microorganisms when nitrate was supplied as an electron acceptor. Aromatic acids with two or more methyl substituants on the benzene ring persisted under nitrate-reducing conditions. Although iron reduction and sulfate reduction were important processes in situ and occurred in the microcosms, these reactions were not coupled to the biological oxidation of aromatic organic acids that were added to the microcosms as electron donors. ?? 1995 American Chemical Society.

Anaerobic electron acceptor chemotaxis in Shewanella putrefaciens

NASA Technical Reports Server (NTRS)

Nealson, K. H.; Moser, D. P.; Saffarini, D. A.

1995-01-01

Shewanella putrefaciens MR-1 can grow either aerobically or anaerobically at the expense of many different electron acceptors and is often found in abundance at redox interfaces in nature. Such redox interfaces are often characterized by very strong gradients of electron acceptors resulting from rapid microbial metabolism. The coincidence of S. putrefaciens abundance with environmental gradients prompted an examination of the ability of MR-1 to sense and respond to electron acceptor gradients in the laboratory. In these experiments, taxis to the majority of the electron acceptors that S. putrefaciens utilizes for anaerobic growth was seen. All anaerobic electron acceptor taxis was eliminated by the presence of oxygen, nitrate, nitrite, elemental sulfur, or dimethyl sulfoxide, even though taxis to the latter was very weak and nitrate and nitrite respiration was normal in the presence of dimethyl sulfoxide. Studies with respiratory mutants of MR-1 revealed that several electron acceptors that could not be used for anaerobic growth nevertheless elicited normal anaerobic taxis. Mutant M56, which was unable to respire nitrite, showed normal taxis to nitrite, as well as the inhibition of taxis to other electron acceptors by nitrite. These results indicate that electron acceptor taxis in S. putrefaciens does not conform to the paradigm established for Escherichia coli and several other bacteria. Carbon chemo-taxis was also unusual in this organism: of all carbon compounds tested, the only positive response observed was to formate under anaerobic conditions.

Non-fullerene electron acceptors for organic photovoltaic devices

DOE Office of Scientific and Technical Information (OSTI.GOV)

Jenekhe, Samson A.; Li, Haiyan; Earmme, Taeshik

Non-fullerene electron acceptors for highly efficient organic photovoltaic devices are described. The non-fullerene electron acceptors have an extended, rigid, .pi.-conjugated electron-deficient framework that can facilitate exciton and charge derealization. The non-fullerene electron acceptors can physically mix with a donor polymer and facilitate improved electron transport. The non-fullerene electron acceptors can be incorporated into organic electronic devices, such as photovoltaic cells.

Acidities of Water and Methanol in Aqueous Solution and DMSO

ERIC Educational Resources Information Center

Gao, Daqing

2009-01-01

The relative acidities of water and methanol have been a nagging issue. In gas phase, methanol is more acidic than water by 36.0 kJ/mol; however, in aqueous solution, the acidities of methanol and water are almost identical. The acidity of an acid in solution is determined by both the intrinsic gas-phase ionization Gibbs energy and the solvent…

Local Intermolecular Order Controls Photoinduced Charge Separation at Donor/Acceptor Interfaces in Organic Semiconductors

DOE Office of Scientific and Technical Information (OSTI.GOV)

Feier, Hilary M.; Reid, Obadiah G.; Pace, Natalie A.

2016-03-23

How free charge is generated at organic donor-acceptor interfaces is an important question, as the binding energy of the lowest energy (localized) charge transfer states should be too high for the electron and hole to escape each other. Recently, it has been proposed that delocalization of the electronic states participating in charge transfer is crucial, and aggregated or otherwise locally ordered structures of the donor or the acceptor are the precondition for this electronic characteristic. The effect of intermolecular aggregation of both the polymer donor and fullerene acceptor on charge separation is studied. In the first case, the dilute electronmore » acceptor triethylsilylhydroxy-1,4,8,11,15,18,22,25-octabutoxyphthalocyaninatosilicon(IV) (SiPc) is used to eliminate the influence of acceptor aggregation, and control polymer order through side-chain regioregularity, comparing charge generation in 96% regioregular (RR-) poly(3-hexylthiophene) (P3HT) with its regiorandom (RRa-) counterpart. In the second case, ordered phases in the polymer are eliminated by using RRa-P3HT, and phenyl-C61-butyric acid methyl ester (PC61BM) is used as the acceptor, varying its concentration to control aggregation. Time-resolved microwave conductivity, time-resolved photoluminescence, and transient absorption spectroscopy measurements show that while ultrafast charge transfer occurs in all samples, long-lived charge carriers are only produced in films with intermolecular aggregates of either RR-P3HT or PC61BM, and that polymer aggregates are just as effective in this regard as those of fullerenes.« less

Calcium leaching behavior of cementitious materials in hydrochloric acid solution.

PubMed

Yang, Huashan; Che, Yujun; Leng, Faguang

2018-06-11

The calcium leaching behavior of cement paste and silica fume modified calcium hydroxide paste, exposed to hydrochloric acid solution, is reported in this paper. The kinetic of degradation was assessed by the changes of pH of hydrochloric acid solution with time. The changes of compressive strength of specimens in hydrochloric acid with time were tested. Hydration products of leached specimens were also analyzed by X-ray diffraction (XRD), differential scanning calorimetry (DSC), thermogravimetric (TG), and atomic force microscope (AFM). Tests results show that there is a dynamic equilibrium in the supply and consumption of calcium hydroxide in hydrochloric acid solution, which govern the stability of hydration products such as calcium silicate hydrate (C-S-H). The decrease of compressive strength indicates that C-S-H are decomposed due to the lower concentration of calcium hydroxide in the pore solution than the equilibrium concentration of the hydration products. Furthermore, the hydration of unhydrated clinker delayed the decomposition of C-S-H in hydrochloric acid solution due to the increase of calcium hydroxide in pore solution of cementitious materials.

Oligomerization of L-gamma-carboxyglutamic acid

NASA Technical Reports Server (NTRS)

Hill, A. R. Jr; Orgel, L. E.; Bada, J. L. (Principal Investigator)

1999-01-01

Unlike glutamic acid, L-gamma-carboxyglutamic acid does not oligomerize efficiently when treated with carbonyldiimidazole in aqueous solution. However, divalent ions such as Mg2+ catalyze the reaction, and lead to the formation of oligomers in good yield. In the presence of hydroxylapatite, L-gamma-carboxyglutamic acid oligomerizes efficiently in a reaction that proceeds in the absence of divalent ions but is further catalyzed when they are present. After 'feeding' 50 times with activated amino acid in the presence of the Mg2+ ion, oligomers longer than the 20-mer could be detected. The effect of hydroxylapatite on peptide elongation is very sensitive to the nature of the activated amino acid and the acceptor peptide. Glutamic acid oligomerizes more efficiently than L-gamma-carboxyglutamic acid on hydroxylapatite and adds more efficiently to decaglutamic acid in solution. One might, therefore, expect that glutamic acid would add more efficiently than L-gamma-carboxyglutamic acid to decaglutamic acid on hydroxylapatite. The contrary is true--the addition of L-gamma-carboxyglutamic acid is substantially more efficient. This suggests that oligomerization on the surface of hydroxylapatite depends on the detailed match between the structure of the surface of the mineral and the structure of the oligomer.

Reactions of vitamin A with acceptors of electrons. Interactions with iodine and the formation of iodide

PubMed Central

Lucy, J. A.; Lichti, F. Ulrike

1969-01-01

1. The reactions of retinol and retinoic acid with iodine were investigated since knowledge of the chemical reactions of vitamin A with acceptors of electrons may shed light on its biochemical mode of action. 2. Colloidal retinol, but not retinoic acid, reacts with iodine to yield a blue–green complex that rapidly decomposes, giving iodide and an unknown species with λmax. at 870mμ. 3. In addition, both retinol and retinoic acid reduce iodine to iodide by a reaction that does not involve an intermediate coloured complex; this reaction appears to yield unstable carbonium ion derivatives of the vitamin. 4. The presence of water greatly facilitates the production of iodide from vitamin A and iodine. 5. Possible chemical pathways involved in these reactions are discussed. 6. It is suggested that the chemical properties of retinol and retinoic acid that underlie their biochemical behaviour might be apparent only when the molecules are at a lipid–water interface, and that vitamin A might be expected to react with a number of different electron acceptors in vivo. PMID:5801297

Population and size distribution of solute-rich mesospecies within mesostructured aqueous amino acid solutions.

PubMed

Jawor-Baczynska, Anna; Moore, Barry D; Lee, Han Seung; McCormick, Alon V; Sefcik, Jan

2013-01-01

Aqueous solutions of highly soluble substances such as small amino acids are usually assumed to be essentially homogenous systems with some degree of short range local structuring due to specific interactions on the sub-nanometre scale (e.g. molecular clusters, hydration shells), usually not exceeding several solute molecules. However, recent theoretical and experimental studies have indicated the presence of much larger supramolecular assemblies or mesospecies in solutions of small organic and inorganic molecules as well as proteins. We investigated both supersaturated and undersaturated aqueous solutions of two simple amino acids (glycine and DL-alanine) using Dynamic Light Scattering (DLS), Brownian Microscopy/Nanoparticles Tracking Analysis (NTA) and Cryogenic Transmission Electron Microscopy (Cryo-TEM). Colloidal scale mesospecies (nanodroplets) were previously reported in supersaturated solutions of these amino acids and were implicated as intermediate species on non-classical crystallization pathways. Surprisingly, we have found that the mesospecies are also present in significant numbers in undersaturated solutions even when the solute concentration is well below the solid-liquid equilibrium concentration (saturation limit). Thus, mesopecies can be observed with mean diameters ranging from 100 to 300 nm and a size distribution that broadens towards larger size with increasing solute concentration. We note that the mesospecies are not a separate phase and the system is better described as a thermodynamically stable mesostructured liquid containing solute-rich domains dispersed within bulk solute solution. At a given temperature, solute molecules in such a mesostructured liquid phase are subject to equilibrium distribution between solute-rich mesospecies and the surrounding bulk solution.

Fullerene-bisadduct acceptors for polymer solar cells.

PubMed

Li, Yongfang

2013-10-01

Polymer solar cells (PSCs) have drawn great attention in recent years for their simple device structure, light weight, and low-cost fabrication in comparison with inorganic semiconductor solar cells. However, the power-conversion efficiency (PCE) of PSCs needs to be increased for their future application. The key issue for improving the PCE of PSCs is the design and synthesis of high-efficiency conjugated polymer donors and fullerene acceptors for the photovoltaic materials. For the acceptor materials, several fullerene-bisadduct acceptors with high LUMO energy levels have demonstrated excellent photovoltaic performance in PSCs with P3HT as a donor. In this Focus Review, recent progress in high-efficiency fullerene-bisadduct acceptors is discussed, including the bisadduct of PCBM, indene-C60 bisadduct (ICBA), indene-C70 bisadduct (IC70BA), DMPCBA, NCBA, and bisTOQC. The LUMO levels and photovoltaic performance of these bisadduct acceptors with P3HT as a donor are summarized and compared. In addition, the applications of an ICBA acceptor in new device structures and with other conjugated polymer donors than P3HT are also introduced and discussed. Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Compatible solute influence on nucleic acids: Many questions but few answers

PubMed Central

Kurz, Matthias

2008-01-01

Compatible solutes are small organic osmolytes including but not limited to sugars, polyols, amino acids, and their derivatives. They are compatible with cell metabolism even at molar concentrations. A variety of organisms synthesize or take up compatible solutes for adaptation to extreme environments. In addition to their protective action on whole cells, compatible solutes display significant effects on biomolecules in vitro. These include stabilization of native protein and nucleic acid structures. They are used as additives in polymerase chain reactions to increase product yield and specificity, but also in other nucleic acid and protein applications. Interactions of compatible solutes with nucleic acids and protein-nucleic acid complexes are much less understood than the corresponding interactions of compatible solutes with proteins. Although we may begin to understand solute/nucleic acid interactions there are only few answers to the many questions we have. I summarize here the current state of knowledge and discuss possible molecular mechanisms and thermodynamics. PMID:18522725

Synthetic CO.sub.2 acceptor

DOEpatents

Lancet, Michael S.; Curran, George P.

1981-08-18

A synthetic CO.sub.2 acceptor consisting essentially of at least one compound selected from the group consisting of calcium oxide and calcium carbonate supported in a refractory carrier matrix, the carrier having the general formula Ca.sub.5 (SiO.sub.4).sub.2 CO.sub.3. A method for producing the synthetic CO.sub.2 acceptor is also disclosed.

The interaction of C.I. acid red 27 with human hemoglobin in solution.

PubMed

Wang, Yan-Qing; Zhang, Hong-Mei; Tang, Bo-Ping

2010-08-02

The nature of the interaction between human hemoglobin and C.I. acid red 27 was investigated systematically by ultraviolet-vis absorbance, circular dichroism, fluorescence, synchronous fluorescence, and three-dimensional fluorescence spectra techniques at pH 7.40. The quenching mechanism, binding constants, and the number of binding sites were determined by the quenching of human hemoglobin fluorescence in presence of C.I. acid red 27. The results showed that the nature of the quenching was of static type and the process of binding acid red 27 on human hemoglobin was a spontaneous molecular interaction procedure. The electrostatic and hydrophobic interactions played a major role in stabilizing the complex; The distance r between donor and acceptor was obtained to be 4.40 nm according to Förster's theory; The effect of acid red 27 on the conformation of human hemoglobin was analyzed using synchronous fluorescence, circular dichroism and three-dimensional fluorescence spectra. 2010 Elsevier B.V. All rights reserved.

Process for the recovery of strontium from acid solutions

DOEpatents

Horwitz, E. Philip; Dietz, Mark L.

1992-01-01

The invention is a process for selectively extracting strontium and technetium values from aqueous nitric acid waste solutions containing these and other fission product values. The extractant is a macrocyclic polyether in a diluent which is insoluble in water, but which will itself dissolve a small amount of water. The process will extract strontium and technetium values from nitric acid solutions which are up to 6 molar in nitric acid.

A detailed experimental and theoretical investigation of the role of cyano groups in the π-bridged acceptor of sensitizers for use in dye-sensitized solar cells (DSCs).

PubMed

Xu, Qinqin; Yang, Guang; Ren, Yu; Lu, Futai; Zhang, Nuonuo; Qamar, Muhammad; Yang, Manlin; Zhang, Bao; Feng, Yaqing

2017-11-01

Three donor-π conjugated unit-acceptor (D-π-A) type zinc porphyrin sensitizers LX1, LX2 and LX3 bearing meso acrylic acid, α-cyanoacrylic acid, and α-cyanopentadienoic acid, respectively, as the π-bridged acceptors were designed and synthesized for use in dye-sensitized solar cells (DSCs). The interesting role of the cyano group attached to the α position of the acrylic and pentadienoic acid acceptor was investigated. It was shown that even though the introduction of the cyano group and the elongation of the π-bridge can both increase the light-harvesting as indicated by the UV-vis absorption spectra, the relevant cell performance dropped significantly. The photo to power conversion efficiencies (PCEs) of the devices increase in the order of LX1 > LX2 > LX3, with the highest PCE of 6.04% achieved for the LX1-based cell, which bears acrylic acid as the π-bridged acceptor. To further explore the effect of -CN and -CH[double bond, length as m-dash]CH- on the interaction between the absorbed dye and TiO 2 substrates, their density of states (DOS) and partial density of states (PDOS), as well as electronic properties were investigated in detail using theoretical calculations. The results suggest that introducing the -CN group into the acceptor and extending the conjugation of the π-bridge have decreased the LUMO levels of the dyes, leading to weak interfacial coupling, low electron injection driving force, low J sc , and thus poor cell performance.

Dihydrogenphosphate recognition: Assistance from the acidic OH moiety of the anion

NASA Astrophysics Data System (ADS)

Das, Rituraj; Pathak, Nibedan; Choudhury, Samarjit; Borah, Suchibrata; Mahanta, Sanjeev Pran

2017-11-01

The binding affinity of the acidic hydrogen i.e. OH moiety of dihydrogenphosphate was investigated with receptors having competent H-bond donor and H-bond acceptor component. Three derivatives of 2, 3-dipyrrol-2‧-ylquinoxaline substituted with H-bond acceptor moiety at pyrrole α- positions were synthesized and their dihydrogenphosphate affinity was studied. All the three receptors shows general affinity towards fluoride, acetate and cyanide ions in DMSO solution. Interestingly, formyl substitution at both the pyrrole α-positions of 2, 3-dipyrrol-2‧-ylquinoxaline leads to binding of H2PO4-. 1H-NMR study rules out the involvement of the H-bond donor unit of the receptor in the biding event and reveals that the binding occurs predominantly via the Osbnd H⋯O interaction between the acidic OH moiety of the anion and the Cdbnd O of the formyl group of the receptor.

New anthracene derivatives as triplet acceptors for efficient green-to-blue low-power upconversion.

PubMed

Liang, Zuo-Qin; Sun, Bin; Ye, Chang-Qing; Wang, Xiao-Mei; Tao, Xu-Tang; Wang, Qin-Hua; Ding, Ping; Wang, Bao; Wang, Jing-Jing

2013-10-21

Three new anthracene derivatives [2-chloro-9,10-dip-tolylanthracene (DTACl), 9,10-dip-tolylanthracene-2-carbonitrile (DTACN), and 9,10-di(naphthalen-1-yl)anthracene-2-carbonitrile (DNACN)] were synthesized as triplet acceptors for low-power upconversion. Their linear absorption, single-photon-excited fluorescence, and upconversion fluorescence properties were studied. The acceptors exhibit high fluorescence yields in DMF. Selective excitation of the sensitizer Pd(II)octaethylporphyrin (PdOEP) in solution containing DTACl, DTACN, or DNA-CN at 532 nm with an ultralow excitation power density of 0.5 W cm(-2) results in anti-Stokes blue emission. The maximum upconversion quantum yield (Φ(UC) =17.4%) was obtained for the couple PdOEP/DTACl. In addition, the efficiency of the triplet-triplet energy transfer process was quantitatively studied by quenching experiments. Experimental results revealed that a highly effective acceptor for upconversion should combine high fluorescence quantum yields with efficient quenching of the sensitizer triplet. Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Process for the recovery of strontium from acid solutions

DOEpatents

Horwitz, E.P.; Dietz, M.L.

1992-03-31

The invention is a process for selectively extracting strontium and technetium values from aqueous nitric acid waste solutions containing these and other fission product values. The extractant is a macrocyclic polyether in a diluent which is insoluble in water, but which will itself dissolve a small amount of water. The process will extract strontium and technetium values from nitric acid solutions which are up to 6 molar in nitric acid. 5 figs.

Dibutyl Phosphoric Acid Solubility in High-Acid, Uranium-Bearing Solutions at SRS

DOE Office of Scientific and Technical Information (OSTI.GOV)

Pierce, R.A.

1998-10-02

The Savannah River Site has enriched uranium (EU) solution which has been stored for almost 10 years since being purified in the second uranium cycle of the H area solvent extraction process. The concentrations in solution are approximately 6 g/L U and about 0.1 M nitric acid. Residual tributylphosphate in the solutions has slowly hydrolyzed to form dibutyl phosphoric acid (HDBP) at concentrations averaging 50 mg/L. Uranium is known to form compounds with the dibutylphosphate ion (DBP) which have limited solubility. The potential to form uranium-DBP solids raises a nuclear criticality safety issue. Prior SRTC tests (WSRC-TR-98-00188) showed that U-DBPmore » solids precipitate at concentrations potentially attainable during the storage of enriched uranium solutions. Furthermore, evaporation of the existing EUS solution without additional acidification could result in the precipitation of U-DBP solids if the DBP concentration in the resulting solution exceeds 110 mg/L at ambient temperature. The same potential exists for evaporation of unwashed 1CU solutions. As a follow-up to the earlier studies, SRTC studied the solubility limits for solutions containing acid concentrations above 0.5M HNO3. The data obtained in these tests reveals a shift to higher levels of DBP solubility above 0.5M HNO3 for both 6 g/L and 12 g/L uranium solutions. Analysis of U-DBP solids from the tests identified a mixture of different molecular structures for the solids created. The analysis distinguished UO2(DBP)2 as the dominant compound present at low acid concentrations. As the acid concentration increases, the crystalline UO2(DBP)2 shows molecular substitutions and an increase in amorphous content. Further analysis by methods not available at SRS will be needed to better identify the specific compounds present. This data indicates that acidification prior to evaporation can be used to increase the margin of safety for the storage of the EUS solutions. Subsequent experimentation evaluated

Calculations of acceptor ionization energies in GaN

NASA Astrophysics Data System (ADS)

Wang, H.; Chen, A.-B.

2001-03-01

The k.p Hamiltonian and a model potential are used to deduce the acceptor ionization energies in GaN from a systematic study of the chemical trend in GaAs, GaP, and InP. The acceptors studied include Be, Mg, Ca, Zn, and Cd on the cation sites and C, Si, and Ge on the anion sites. Our calculated acceptor ionization energies are estimated to be accurate to better than 10% across the board. The ionization energies of C and Be (152 and 187 meV, respectively) in wurtzite GaN are found to be lower than that of Mg (224 meV). The C was found to behave like the hydrogenic acceptor in all systems and it has the smallest ionization energy among all the acceptors studied.

Photoinduced electron transfer across a molecular wall: coumarin dyes as donors and methyl viologen and TiO2 as acceptors.

PubMed

Porel, Mintu; Klimczak, Agnieszka; Freitag, Marina; Galoppini, Elena; Ramamurthy, V

2012-02-21

Coumarins C-153, C-480, and C-1 formed 1:2 (guest:host) complexes with a water-soluble cavitand having eight carboxylic acid groups (OA) in aqueous borate buffer solution. The complexes were photoexcited in the presence of electron acceptors (methyl viologen, MV(2+), or TiO(2)) to probe the possibility of electron transfer between a donor and an acceptor physically separated by a molecular wall. In solution at basic pH, the dication MV(2+) was associated to the exterior of the complex C-153@OA(2), as suggested by diffusion constants (~1.2 × 10(-6) cm(2)/s) determined by DOSY NMR. The fluorescence of C-153@OA(2) was quenched in the presence of increasing amounts of MV(2+) and Stern-Volmer plots of I(o)/I and τ(o)/τ vs [MV(2+)] indicated that the quenching was static. As per FT-IR-ATR spectra, the capsule C-153@OA(2) was bound to TiO(2) nanoparticle films. Selective excitation (λ(exc) = 420) of the above bound complex resulted in fluorescence quenching. When adsorbed on insulating ZrO(2) nanoparticle films, excitation of the complex resulted in a broad fluorescence spectrum centered at 500 nm and consistent with C-153 being within the lipophilic capsule interior. Consistent with the above results, colloidal TiO(2) quenched the emission while colloidal ZrO(2) did not.

Transpeptidation reactions of a specific substrate catalyzed by the streptomyces R61 DD-peptidase: characterization of a chromogenic substrate and acyl acceptor design.

PubMed

Kumar, Ish; Pratt, R F

2005-08-02

The Streptomyces R61 dd-peptidase, a functional model for penicillin-binding proteins, catalyzes the hydrolysis and aminolysis of d-alanyl-d-alanine-terminating peptides by specific amines. In vivo, this reaction completes bacterial cell wall biosynthesis. For in vitro studies of this enzyme to date, various nonspecific acyl-donor substrates have been employed. Recently, however, a peptidoglycan-mimetic peptide substrate, glycyl-l-alpha-amino-epsilon-pimelyl-d-alanyl-d-alanine, has been described that is much more specific for this enzyme. In this paper, we describe the synthesis and kinetic characterization of an analogous thiolester substrate, 3-(N-glycyl-l-cysteinyl)-propanoyl-d-alanyl-d-thiolactate, that the enzyme hydrolyzes and aminolyzes very efficiently (k(cat)/K(m) = 1.0 x 10(7) s(-)(1) M(-)(1)). Direct or indirect, by means of a thiol trap, spectrophotometric monitoring of the reactions of this substrate is readily achieved. Deacylation of the enzyme is rate-determining under substrate saturation conditions, and therefore the aminolysis reaction can be directly studied. The results show that d-amino acids and certain Gly-l-Xaa dipeptides and tripeptides may act as acyl acceptors at the active site of the enzyme. d-Phenylalanine and Gly-l-Phe were the most effective d-amino acid and dipeptide acceptors, respectively. On the basis of the dual specificity of the active site for acceptors (d-amino acids and Gly-l-Xaa peptides), "dual function" acceptors were designed and synthesized. Two of these, aminomalon-(N-ethyl)amide and aminomalon-(N-phenethyl)amide, were particularly effective. It did seem, however, that the observed rates of reaction of these very effective acceptors may be limited by some common, possibly physical, step. More extended, peptidoglycan-like, acceptors were found to be essentially unreactive. The reasons for this counterintuitive behavior are discussed.

Process for the removal of radium from acidic solutions containing same

DOEpatents

Scheitlin, F.M.

The invention is a process for the removal of radium from acidic aqueous solutions. In one aspect, the invention is a process for removing radium from an inorganic-acid solution. The process comprises contacting the solution with coal fly ash to effect adsorption of the radium on the ash. The radium-containing ash then is separated from the solution. The process is simple, comparatively inexpensive, and efficient. High radium-distribution coefficients are obtained even at room temperature. Coal fly ash is an inexpensive, acid-resistant, high-surface-area material which is available in large quantities throughout the United States. The invention is applicable, for example, to the recovery of /sup 226/Ra from nitric acid solutions which have been used to leach radium from uranium-mill tailings.

Acceptors in bulk and nanoscale ZnO

NASA Astrophysics Data System (ADS)

McCluskey, M. D.

2012-02-01

Zinc oxide (ZnO) is a semiconductor that emits bright UV light, with little wasted heat. This intrinsic feature makes it a promising material for energy-efficient white lighting, nano-lasers, and other optical applications. For devices to be competitive, however, it is necessary to develop reliable p-type doping. Although substitutional nitrogen has been considered as a potential p-type dopant for ZnO, theoretical and experimental work indicates that nitrogen is a deep acceptor and will not lead to p-type conductivity. This talk will highlight recent experiments on ZnO:N at low temperatures. A red/near-IR photoluminescence (PL) band is correlated with the presence of deep nitrogen acceptors. PL excitation (PLE) measurements show an absorption threshold of 2.26 eV, in good agreement with theory. Magnetic resonance experiments provide further evidence for this assignment. The results of these studies seem to rule out group-V elements as shallow acceptors in ZnO, contradicting numerous reports in the literature. If these acceptors do not work as advertised, is there a viable alternative? Optical studies on ZnO nanocrystals show some intriguing leads. At liquid-helium temperatures, a series of sharp IR absorption peaks arise from an unknown acceptor impurity. The data are consistent with a hydrogenic acceptor 0.46 eV above the valence band edge. While this binding energy is still too deep for many practical applications, it represents a significant improvement over the ˜ 1.3 eV binding energy for nitrogen acceptors. Nanocrystals present another twist. Due to their high surface-to-volume ratio, surface states are especially important. Specifically, electron-hole recombination at the surface give rises to a red luminescence band. From our PL and IR experiments, we have developed a ``unified'' model that attempts to explain acceptor and surface states in ZnO nanocrystals. This model could provide a useful framework for designing future nanoscale ZnO devices.

Chemical trends for acceptor impurities in GaN

NASA Astrophysics Data System (ADS)

Neugebauer, Jörg; Van de Walle, Chris G.

1999-03-01

We present a comprehensive investigation of acceptor impurities in GaN, based on first-principles total-energy calculations. Two main factors are identified that determine acceptor incorporation: the strength of chemical bonding between the acceptor and its neighbors (which can be assessed by comparison with existing compounds) and the atomic size match between the acceptor and the host atom for which it substitutes. None of the candidates (Li, Na, K, Be, Zn, and Ca) exhibits characteristics which surpass those of Mg in all respects. Only Be emerges as a potential alternative dopant, although it may suffer from compensation by Be interstitial donors.

Effective Tuning of Ketocyanine Derivatives through Acceptor Substitution.

PubMed

Poe, Ambata; Della Pelle, Andrea; Byrnes, Sean; Thayumanavan, S

2015-05-18

A series of ketocyanine derivatives possessing bis(diarylamino)fluorenyl donors and variable acceptors installed at the bridging carbon atom were synthesized to investigate how the electronic structure of the dye can be systemically tuned through stabilization of the cyanine-like character of the donor by increasing the acceptor strength. Analysis of the (1) H NMR spectra indicates that the "charge-separated" species dominates in these dyes, given that carbons possessing a positive or negative charge in the resonance structures of this state purposefully shift downfield or upfield, respectively, depending on the strength of the acceptor moiety. In DAA-Fl-PI, the acceptor strength and the gain of acceptor aromaticity indicates a predisposition of the separated state, indicated by asymmetry in the (1) H NMR spectrum, as well as uneven distribution of the HOMO on the fluorenyl donor. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Electromembrane extraction using two separate cells: A new design for simultaneous extraction of acidic and basic compounds.

PubMed

Nojavan, Saeed; Asadi, Sakine

2016-02-01

Simultaneous extraction of acidic and basic analytes from a sample is seen to be a challenging task. In this work, a novel and efficient electromembrane extraction (EME) method based on two separate cells was applied to simultaneously extract and preconcentrate two acidic drugs (naproxen and ibuprofen) along with a basic drug (ketamine). Once both cells were filled with the sample solution, basic drug was extracted from one cell with the other cell used to extract acidic drugs. The employed supported liquid membranes for the extraction of acidic and basic drugs were 2-ethyl hexanol and 1-octanol, respectively. Under an applied potential of 250 V in the course of the extraction process, acidic, and basic drugs were extracted from a 3.0 mL aqueous sample solution into 25 μL acceptor solutions. The pH values of the donor and acceptor solutions in the cathodic cell were 5.0 and 1.5, respectively, the corresponding values in the anodic cell were, however, 8.0 and 12.5, respectively. The rates of recovery obtained within 20 min of extraction time at a stirring rate of 750 rpm ranged from 45 to 54%. With correlation coefficients ranging from 0.990 to 0.996, the proposed EME technique provided good linearity over a concentration range of 20-1000 ng/mL. The LOD for all drugs was found to be 6.7 ng/mL, while reproducibility ranged from 7 to 12% (n = 5). Finally, applying the proposed method to determine and quantify the drugs in urine and wastewater samples, satisfactory results were achieved. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Electron Affinity of Phenyl-C61-Butyric Acid Methyl Ester (PCBM)

DOE Office of Scientific and Technical Information (OSTI.GOV)

Larson, Bryon W.; Whitaker, James B.; Wang, Xue B.

2013-07-25

The gas-phase electron affinity (EA) of phenyl-C61-butyric acid methyl ester (PCBM), one of the best-performing electron acceptors in organic photovoltaic devices, is measured by lowtemperature photoelectron spectroscopy for the first time. The obtained value of 2.63(1) eV is only ca. 0.05 eV lower than that of C60 (2.68(1) eV), compared to a 0.09 V difference in their E1/2 values measured in this work by cyclic voltammetry. Literature E(LUMO) values for PCBM that are typically estimated from cyclic voltammetry, and commonly used as a quantitative measure of acceptor properties, are dispersed over a wide range between -4.3 and -3.62 eV; themore » reasons for such a huge discrepancy are analyzed here, and the protocol for reliable and consistent estimations of relative fullerene-based acceptor strength in solution is proposed.« less

48-spot single-molecule FRET setup with periodic acceptor excitation

NASA Astrophysics Data System (ADS)

Ingargiola, Antonino; Segal, Maya; Gulinatti, Angelo; Rech, Ivan; Labanca, Ivan; Maccagnani, Piera; Ghioni, Massimo; Weiss, Shimon; Michalet, Xavier

2018-03-01

Single-molecule Förster resonance energy transfer (smFRET) allows measuring distances between donor and acceptor fluorophores on the 3-10 nm range. Solution-based smFRET allows measurement of binding-unbinding events or conformational changes of dye-labeled biomolecules without ensemble averaging and free from surface perturbations. When employing dual (or multi) laser excitation, smFRET allows resolving the number of fluorescent labels on each molecule, greatly enhancing the ability to study heterogeneous samples. A major drawback to solution-based smFRET is the low throughput, which renders repetitive measurements expensive and hinders the ability to study kinetic phenomena in real-time. Here we demonstrate a high-throughput smFRET system that multiplexes acquisition by using 48 excitation spots and two 48-pixel single-photon avalanche diode array detectors. The system employs two excitation lasers allowing separation of species with one or two active fluorophores. The performance of the system is demonstrated on a set of doubly labeled double-stranded DNA oligonucleotides with different distances between donor and acceptor dyes along the DNA duplex. We show that the acquisition time for accurate subpopulation identification is reduced from several minutes to seconds, opening the way to high-throughput screening applications and real-time kinetics studies of enzymatic reactions such as DNA transcription by bacterial RNA polymerase.

The role of amino acid electron-donor/acceptor atoms in host-cell binding peptides is associated with their 3D structure and HLA-binding capacity in sterile malarial immunity induction

DOE Office of Scientific and Technical Information (OSTI.GOV)

Patarroyo, Manuel E., E-mail: mepatarr@mail.com; Universidad Nacional de Colombia, Bogota; Almonacid, Hannia

Highlights: Black-Right-Pointing-Pointer Fundamental residues located in some HABPs are associated with their 3D structure. Black-Right-Pointing-Pointer Electron-donor atoms present in {beta}-turn, random, distorted {alpha}-helix structures. Black-Right-Pointing-Pointer Electron-donor atoms bound to HLA-DR53. Black-Right-Pointing-Pointer Electron-acceptor atoms present in regular {alpha}-helix structure bound to HLA-DR52. -- Abstract: Plasmodium falciparum malaria continues being one of the parasitic diseases causing the highest worldwide mortality due to the parasite's multiple evasion mechanisms, such as immunological silence. Membrane and organelle proteins are used during invasion for interactions mediated by high binding ability peptides (HABPs); these have amino acids which establish hydrogen bonds between them in some of theirmore » critical binding residues. Immunisation assays in the Aotus model using HABPs whose critical residues had been modified have revealed a conformational change thereby enabling a protection-inducing response. This has improved fitting within HLA-DR{beta}1{sup Asterisk-Operator} molecules where amino acid electron-donor atoms present in {beta}-turn, random or distorted {alpha}-helix structures preferentially bound to HLA-DR53 molecules, whilst HABPs having amino acid electron-acceptor atoms present in regular {alpha}-helix structure bound to HLA-DR52. This data has great implications for vaccine development.« less

Femtosecond-picosecond laser photolysis studies on the dynamics of excited charge-transfer complexes: Aromatic hydrocarbon-acid anhydride, -tetracyanoethylene, and -tetracyanoquinodimethane systems in acetonitrile solutions

DOE Office of Scientific and Technical Information (OSTI.GOV)

Asahi, Tsuyoshi; Mataga, Noboru

1991-03-07

Formation processes of contact ion pairs (CIP) from the excited Franck-Condon (FC) state of charge-transfer (CT) complexes of aromatic hydrocarbons with acid anhydride as well as cyano compound acceptors in acetonitrile solution and charge recombination (CR) rates (k{sub CR}{sup CIP}) of produced CIP states have been investigated by femtosecond and picosecond laser phototlysis and time-resolved absorption spectral measurements covering a wide range of free energy gap-{Delta}G{degree}{sub ip} between the ion pair and the ground state. It has been confirmed that the CIP formation becomes faster and k{sub CR}{sup CIP} of the produced CIP increases with increase of the strengths ofmore » the electron donor (D) and acceptor (A) in the complex, i.e., with decrease of the {minus}{Delta}G{degree}{sub ip} value. This peculiar energy gap dependence of k{sub CR}{sup CIP}, quite different from the bell-shaped one observed in the case of the solvent-separated ion pairs (SSIP) or loose ion pairs (LIP) formed by encounter between fluorescer and quencher in the fluoresence quenching reaction, has been interpreted by assuming the change of electronic and geometrical structures of CIP depending on the strengths of D and A.« less

Cyan-emitting and orange-emitting fluorescent proteins as a donor/acceptor pair for fluorescence resonance energy transfer.

PubMed

Karasawa, Satoshi; Araki, Toshio; Nagai, Takeharu; Mizuno, Hideaki; Miyawaki, Atsushi

2004-07-01

GFP (green fluorescent protein)-based FRET (fluorescence resonance energy transfer) technology has facilitated the exploration of the spatio-temporal patterns of cellular signalling. While most studies have used cyan- and yellow-emitting FPs (fluorescent proteins) as FRET donors and acceptors respectively, this pair of proteins suffers from problems of pH-sensitivity and bleeding between channels. In the present paper, we demonstrate the use of an alternative additional donor/acceptor pair. We have cloned two genes encoding FPs from stony corals. We isolated a cyan-emitting FP from Acropara sp., whose tentacles exhibit cyan coloration. Similar to GFP from Renilla reniformis, the cyan FP forms a tight dimeric complex. We also discovered an orange-emitting FP from Fungia concinna. As the orange FP exists in a complex oligomeric structure, we converted this protein into a monomeric form through the introduction of three amino acid substitutions, recently reported to be effective for converting DsRed into a monomer (Clontech). We used the cyan FP and monomeric orange FP as a donor/acceptor pair to monitor the activity of caspase 3 during apoptosis. Due to the close spectral overlap of the donor emission and acceptor absorption (a large Förster distance), substantial pH-resistance of the donor fluorescence quantum yield and the acceptor absorbance, as well as good separation of the donor and acceptor signals, the new pair can be used for more effective quantitative FRET imaging.

How localized acceptors limit p-type conductivity in GaN

NASA Astrophysics Data System (ADS)

Lyons, John L.

2013-03-01

Despite the impressive development of GaN as an optoelectronic material, p-type conductivity is still limited. Only a single acceptor impurity, magnesium, is known to lead to p-type GaN. But Mg is far from a well-behaved acceptor. Hydrogen is known to passivate Mg, necessitating a post-growth anneal for acceptor activation. In addition, the ionization energy is quite large (~ 200 meV in GaN), meaning only a few percent of Mg acceptors are ionized at room temperature. Thus, hole conductivity is limited, and high concentrations of Mg are required to achieve moderately p-type GaN. Other acceptor impurities have not proven to be effective p-type dopants, for reasons that are still unresolved. Using advanced first-principles calculations based on a hybrid functional, we investigate the electrical and optical properties of the isolated Mg acceptor and its complexes with hydrogen in GaN, InN, and AlN.[2] We employ a technique that overcomes the band-gap-problem of traditional density functional theory, and allows for quantitative predictions of acceptor ionization energies and optical transition energies. Our results allow us to explain the deep or shallow nature of the Mg acceptor and its relation to the optical signals observed in Mg-doped GaN. We also revisit the properties of other group-II acceptors in GaN. We find that all cation-site acceptors show behavior similar to MgGa, and lead to highly localized holes. The ZnGa and BeGa acceptors have ionization energies that are even larger than that of Mg, making them ineffective dopants. All acceptors cause large lattice distortions in their neutral charge state, in turn leading to deep, broad luminescence signals that can serve as a means of experimentally verifying the deep nature of these acceptors. This work was performed in collaboration with Audrius Alkauskas, Anderson Janotti, and Chris G. Van de Walle. It was supported by the NSF and by the Solid State Lighting and Energy Center at UCSB.

Equilibrium sampling through membranes (ESTM) of acidic organic pollutants using hollow fibre modules in continuous steady-state mode.

PubMed

Larsson, Niklas; Utterback, Karl; Toräng, Lars; Risberg, Johan; Gustafsson, Per; Mayer, Philipp; Jönsson, Jan Ke

2009-08-01

Hollow fibre (HF) membrane modules were applied in continuous mode for equilibrium sampling through membranes (ESTM) of polar organic pollutants. Phenolic compounds (chlorophenols, cresols and phenol) served as model substances and ESTM was tuned towards the measurement of freely dissolved concentrations (C(free)). HF membrane modules were constructed using thin-walled membrane, 1-m module length and low packing density in order to optimise the uptake kinetics of the analytes into the acceptor solution. Such custom made devices were tested and compared to commercially available modules. The former modules performed best for continuous ESTM. The custom made modules provided steady-state equilibrium within 20-40 min and enrichment that was in general agreement with calculated distribution ratios between acceptor and sample. In experiments during which sample concentration was changed, acceptor response time to decreased sample concentration was around 30 min for custom built modules. In the presence of commercial humic acids, analytes showed lower steady-state enrichment, which is due to a decrease in C(free). Continuous ESTM may be automated and is suggested for use in online determination of C(free) of pollutants and studies on sorption of pollutants. Future studies should include optimisation of the membrane liquid and factors regarding the residence time of the acceptor solution in the fibre lumen. Qualitative aspects of DOM should also be included, as natural DOM can be fractionated. C(free) could be correlated to DOM properties that have previously been shown to influence sorption, such as aromaticity, carboxylic acid content and molecular size.

Vibrational studies in aqueous solutions. Part II. The acid oxalate ion and oxalic acid

NASA Astrophysics Data System (ADS)

Shippey, T. A.

1980-08-01

Assignments for oxalic acid in solution are re-examined. A detailed assignment of the IR and Raman spectra of the acid oxalate ion is presented for the first time. Raman spectroscopy is used to study the first ionization of oxalic acid.

Shallow versus deep nature of Mg acceptors in nitride semiconductors

NASA Astrophysics Data System (ADS)

Lyons, John; Janotti, Anderson; van de Walle, Chris G.

2012-02-01

Although Mg doping is the only known method for achieving p-type conductivity in nitride semiconductors, Mg is not a perfect acceptor. Hydrogen is known to passivate the Mg acceptor, necessitating a post-growth anneal for acceptor activation. Furthermore, the acceptor ionization energy of Mg is relatively large (200 meV) in GaN, thus only a few percent of Mg acceptors are ionized at room temperature. Surprisingly, despite the importance of this impurity, open questions remain regarding the nature of the acceptor. Optical and magnetic resonance measurements on Mg-doped GaN indicate intriguing and complex behavior that depends on the growth, doping level, and thermal treatment of the samples. Motivated by these studies, we have revisited this topic by performing first-principles calculations based on a hybrid functional. We investigate the electrical and optical properties of the isolated Mg acceptor and its complexes with hydrogen in GaN, InN, and AlN. With the help of these advanced techniques we explain the deep or shallow nature of the Mg acceptor and its relation to optical signals often seen in Mg-doped GaN. We also explore the properties of the Mg acceptor in InN and AlN, allowing predictions of the behavior of the Mg dopant in ternary nitride alloys.

Reduction of Plutonium in Acidic Solutions by Mesoporous Carbons

DOE PAGES

Parsons-Moss, Tashi; Jones, Stephen; Wang, Jinxiu; ...

2015-12-19

Batch contact experiments with several porous carbon materials showed that carbon solids spontaneously reduce the oxidation state of plutonium in 1-1.5 M acid solutions, without significant adsorption. The final oxidation state and rate of Pu reduction varies with the solution matrix, and also depends on the surface chemistry and surface area of the carbon. It was demonstrated that acidic Pu(VI) solutions can be reduced to Pu(III) by passing through a column of porous carbon particles, offering an easy alternative to electrolysis with a potentiostat.

Structural and spectroscopic characterizations on the charge-transfer interactions of the second generation poly(propylene amine) dendrimers with iodine and picric acid acceptors.

PubMed

El-Sayed, Mohamed Y; Refat, Moamen S

2015-02-25

Herein, this study was focused to get a knowledge about the intermolecular charge transfer complexes between the second generation of poly(propylene amine) dendrimer (PPD2) with picric acid (PA) and iodine (I2) as π and σ-acceptors. The charge-transfer interaction of the PPD2 electron donor and the PA acceptor has been studied in CHCl3. The resulted data refereed to the formation of the new CT-complex with the general formula [(PPD2)(PA)4]. The 1:4 stoichiometry of the reaction was discussed upon the on elemental analysis and photometric titration. On the other hand, the 1:3½ iodine-PPD2 heptaiodide (I7(-)) charge-transfer complex has been studied spectrophotometrically in chloroform at room temperature with general formula [(PPD2)](+)I7(-). The electronic absorption bands of 2I2·I3(-) (I7(-)) are observed at 358 and 294 nm. Raman laser spectrum of the brown solid heptaiodide complex has two clearly vibration bands at 155 and 110 cm(-1) due to symmetric stretching νs(II) outer and inner bonds, respectively. The (1)H NMR spectra and differential scanning calorimetry (DSC) data of PPD2 charge-transfer complexes were discussed. Copyright © 2014 Elsevier B.V. All rights reserved.

Structural and spectroscopic characterizations on the charge-transfer interactions of the second generation poly(propylene amine) dendrimers with iodine and picric acid acceptors

NASA Astrophysics Data System (ADS)

El-Sayed, Mohamed Y.; Refat, Moamen S.

2015-02-01

Herein, this study was focused to get a knowledge about the intermolecular charge transfer complexes between the second generation of poly(propylene amine) dendrimer (PPD2) with picric acid (PA) and iodine (I2) as π and σ-acceptors. The charge-transfer interaction of the PPD2 electron donor and the PA acceptor has been studied in CHCl3. The resulted data refereed to the formation of the new CT-complex with the general formula [(PPD2)(PA)4]. The 1:4 stoichiometry of the reaction was discussed upon the on elemental analysis and photometric titration. On the other hand, the 1:3½ iodine-PPD2 heptaiodide (I7-) charge-transfer complex has been studied spectrophotometrically in chloroform at room temperature with general formula [(PPD2)]+I7-. The electronic absorption bands of 2I2·I3- (I7-) are observed at 358 and 294 nm. Raman laser spectrum of the brown solid heptaiodide complex has two clearly vibration bands at 155 and 110 cm-1 due to symmetric stretching νs(Isbnd I) outer and inner bonds, respectively. The 1H NMR spectra and differential scanning calorimetry (DSC) data of PPD2 charge-transfer complexes were discussed.

Ultrafast electron transfer in all-carbon-based SWCNT-C60 donor-acceptor nanoensembles connected by poly(phenylene-ethynylene) spacers

NASA Astrophysics Data System (ADS)

Barrejón, Myriam; Gobeze, Habtom B.; Gómez-Escalonilla, María J.; Fierro, José Luis G.; Zhang, Minfang; Yudasaka, Masako; Iijima, Sumio; D'Souza, Francis; Langa, Fernando

2016-08-01

Building all-carbon based functional materials for light energy harvesting applications could be a solution to tackle and reduce environmental carbon output. However, development of such all-carbon based donor-acceptor hybrids and demonstration of photoinduced charge separation in such nanohybrids is a challenge since in these hybrids part of the carbon material should act as an electron donating or accepting photosensitizer while the second part should fulfil the role of an electron acceptor or donor. In the present work, we have successfully addressed this issue by synthesizing covalently linked all-carbon-based donor-acceptor nanoensembles using single-walled carbon nanotubes (SWCNTs) as the donor and C60 as the acceptor. The donor-acceptor entities in the nanoensembles were connected by phenylene-ethynylene spacer units to achieve better electronic communication and to vary the distance between the components. These novel SWCNT-C60 nanoensembles have been characterized by a number of techniques, including TGA, FT-IR, Raman, AFM, absorbance and electrochemical methods. The moderate number of fullerene addends present on the side-walls of the nanotubes largely preserved the electronic structure of the nanotubes. The thermodynamic feasibility of charge separation in these nanoensembles was established using spectral and electrochemical data. Finally, occurrence of ultrafast electron transfer from the excited nanotubes in these donor-acceptor nanohybrids has been established by femtosecond transient absorption studies, signifying their utility in building light energy harvesting devices.Building all-carbon based functional materials for light energy harvesting applications could be a solution to tackle and reduce environmental carbon output. However, development of such all-carbon based donor-acceptor hybrids and demonstration of photoinduced charge separation in such nanohybrids is a challenge since in these hybrids part of the carbon material should act as an

Energy bands and acceptor binding energies of GaN

NASA Astrophysics Data System (ADS)

Xia, Jian-Bai; Cheah, K. W.; Wang, Xiao-Liang; Sun, Dian-Zhao; Kong, Mei-Ying

1999-04-01

The energy bands of zinc-blende and wurtzite GaN are calculated with the empirical pseudopotential method, and the pseudopotential parameters for Ga and N atoms are given. The calculated energy bands are in agreement with those obtained by the ab initio method. The effective-mass theory for the semiconductors of wurtzite structure is established, and the effective-mass parameters of GaN for both structures are given. The binding energies of acceptor states are calculated by solving strictly the effective-mass equations. The binding energies of donor and acceptor are 24 and 142 meV for the zinc-blende structure, 20 and 131, and 97 meV for the wurtzite structure, respectively, which are consistent with recent experimental results. It is proposed that there are two kinds of acceptor in wurtzite GaN. One kind is the general acceptor such as C, which substitutes N, which satisfies the effective-mass theory. The other kind of acceptor includes Mg, Zn, Cd, etc., the binding energy of these acceptors is deviated from that given by the effective-mass theory. In this report, wurtzite GaN is grown by the molecular-beam epitaxy method, and the photoluminescence spectra were measured. Three main peaks are assigned to the donor-acceptor transitions from two kinds of acceptors. Some of the transitions were identified as coming from the cubic phase of GaN, which appears randomly within the predominantly hexagonal material.

Spectroscopic and thermal investigations on the charge transfer interaction between risperidone as a schizophrenia drug with some traditional π-acceptors: Part 2

NASA Astrophysics Data System (ADS)

El-Habeeb, Abeer A.; Al-Saif, Foziah A.; Refat, Moamen S.

2013-03-01

The focus of present investigation was to assess the utility of non-expensive techniques in the evaluation of risperidone (Ris) in solid and solution states with different traditional π-acceptors and subsequent incorporation of the analytical determination into pharmaceutical formulation for a faster release of risperidone. Charge-transfer complexes (CTC) of risperidone with picric acid (PA), 2,3-dichloro-5,6-dicyano-p-benzoquinon (DDQ), tetracyanoquinodimethane (TCNQ), tetracyano ethylene (TCNE), tetrabromo-p-quinon (BL) and tetrachloro-p-quinon (CL) have been studied spectrophotometrically in absolute methanol at room temperature. The stoichiometries of the complexes were found to be 1:1 ratio by the photometric molar ratio between risperidone and the π-acceptors. The equilibrium constants, molar extinction coefficient (ɛCT) and spectroscopic-physical parameters (standard free energy (ΔGo), oscillator strength (f), transition dipole moment (μ), resonance energy (RN) and ionization potential (ID)) of the complexes were determined upon the modified Benesi-Hildebrand equation. Risperidone in pure form was applied in this study. The results indicate that the formation constants for the complexes depend on the nature of electron acceptors and donor, and also the spectral studies of the complexes were determined by (infrared, Raman, and 1H NMR) spectra and X-ray powder diffraction (XRD). The most stable mono-protonated form of Ris is characterized by the formation of +Nsbnd H (pyrimidine ring) intramolecular hydrogen bonded. In the high-wavenumber spectral region ˜3400 cm-1, the bands of the +Nsbnd H stretching vibrations and of the pyrimidine nitrogen atom could be potentially useful to discriminate the investigated forms of Ris. The infrared spectra of both Ris complexes are confirming the participation of +Nsbnd H pyrimidine ring in the donor-acceptor interaction.

Solubility of xenon in amino-acid solutions. II. Nine less-soluble amino acids

NASA Astrophysics Data System (ADS)

Kennan, Richard P.; Himm, Jeffrey F.; Pollack, Gerald L.

1988-05-01

Ostwald solubility (L) of xenon gas, as the radioisotope 133Xe, has been measured as a function of solute concentration, at 25.0 °C, in aqueous solutions of nine amino acids. The amino-acid concentrations investigated covered much of their solubility ranges in water, viz., asparagine monohydrate (0-0.19 M), cysteine (0-1.16 M), glutamine (0-0.22 M), histidine (0-0.26 M), isoleucine (0-0.19 M), methionine (0-0.22 M), serine (0-0.38 M), threonine (0-1.4 M), and valine (0-0.34 M). We have previously reported solubility results for aqueous solutions of six other, generally more soluble, amino acids (alanine, arginine, glycine, hydroxyproline, lysine, and proline), of sucrose and sodium chloride. In general, L decreases approximately linearly with increasing solute concentration in these solutions. If we postulate that the observed decreases in gas solubility are due to hydration, the results under some assumptions can be used to calculate hydration numbers (H), i.e., the number of H2O molecules associated with each amino-acid solute molecule. The average values of hydration number (H¯) obtained at 25.0 °C are 15.3±1.5 for asparagine, 6.8±0.3 for cysteine, 11.5±1.1 for glutamine, 7.3±0.7 for histidine, 5.9±0.4 for isoleucine, 10.6±0.8 for methionine, 11.2±1.3 for serine, 7.7± 1.0 for threonine, and 6.6±0.6 for valine. We have also measured the temperature dependence of solubility L(T) from 5-40 °C for arginine, glycine, and proline, and obtained hydration numbers H¯(T) in this range. Between 25-40 °C, arginine has an H¯ near zero. This may be evidence for an attractive interaction between xenon and arginine molecules in aqueous solution.

Raman spectroscopic study of the conformation of dicarboxylic acid salts in aqueous solutions

NASA Astrophysics Data System (ADS)

Fukushima, Kunio; Watanabe, Toshiaki; Umemura, Matome

1986-08-01

It is already known that the molecules of long chain monocarboxylic acid salts have a tendency to form micelles in aqueous solutions, the molecular chain taking the all- trans zigzag structure. However it is considered difficult for dicarboxylic acid salts to adopt the same structure as the monocarboxylic acid salts as they have two carboxyl groups, one on each end of the molecular chain. Therefore, a special structure is expected to exist for dicarboxylic acid salts in aqueous solution. In order to examine this, Raman spectra of suberic acid salt and azelaic acid salt in aqueous solution were measured and the normal vibrational calculation carried out, showing that dicarboxylic acid salts have a helical structure in aqueous solution.

Extraction equilibrium of indium(III) from nitric acid solutions by di(2-ethylhexyl)phosphoric acid dissolved in kerosene.

PubMed

Tsai, Hung-Sheng; Tsai, Teh-Hua

2012-01-04

The extraction equilibrium of indium(III) from a nitric acid solution using di(2-ethylhexyl) phosphoric acid (D2EHPA) as an acidic extractant of organophosphorus compounds dissolved in kerosene was studied. By graphical and numerical analysis, the compositions of indium-D2EHPA complexes in organic phase and stoichiometry of the extraction reaction were examined. Nitric acid solutions with various indium concentrations at 25 °C were used to obtain the equilibrium constant of InR₃ in the organic phase. The experimental results showed that the extraction distribution ratios of indium(III) between the organic phase and the aqueous solution increased when either the pH value of the aqueous solution and/or the concentration of the organic phase extractant increased. Finally, the recovery efficiency of indium(III) in nitric acid was measured.

Organic solar cells based on non-fullerene acceptors

NASA Astrophysics Data System (ADS)

Hou, Jianhui; Inganäs, Olle; Friend, Richard H.; Gao, Feng

2018-02-01

Organic solar cells (OSCs) have been dominated by donor:acceptor blends based on fullerene acceptors for over two decades. This situation has changed recently, with non-fullerene (NF) OSCs developing very quickly. The power conversion efficiencies of NF OSCs have now reached a value of over 13%, which is higher than the best fullerene-based OSCs. NF acceptors show great tunability in absorption spectra and electron energy levels, providing a wide range of new opportunities. The coexistence of low voltage losses and high current generation indicates that new regimes of device physics and photophysics are reached in these systems. This Review highlights these opportunities made possible by NF acceptors, and also discuss the challenges facing the development of NF OSCs for practical applications.

Efficiency of cardioplegic solutions containing L-arginine and L-aspartic acid.

PubMed

Pisarenko, O I; Shul'zhenko, V S; Studneva, I M

2006-04-01

In experiments on rats we studied the effects of cardioplegic solutions with L-aspartic acid or L-arginine on functional recovery and metabolism of isolated working heart after 40-min normothermal global ischemia and 30-min reperfusion. After reperfusion of the hearts preventively protected with cardioplegic solution containing L-aspartic acid or L-arginine, coronary flow decreased in comparison with the initial values. As a component of cardioplegic solution, L-arginine was less efficient in recovery of contractility and cardiac output of the hearts in comparison with L-aspartic acid. In hearts protected with L-aspartic acid, the postischemic levels of ATP and phosphocreatine were significantly higher, and the level of lactate was significantly lower than in hearts protected with L-arginine. In comparison with L-arginine, L-aspartic acid is a more efficient component of cardioplegic solution in protection of the heart from metabolic and functional damages caused by global ischemia and reperfusion.

Hydrogen peroxide generation in a model paediatric parenteral amino acid solution.

PubMed

Brawley, V; Bhatia, J; Karp, W B

1993-12-01

1. Parenteral amino acid solutions undergo photooxidation, which may be an important factor in total parenteral nutrition-associated hepatic dysfunction. Light-exposed parenteral solutions containing amino acids, in addition to vitamins and trace minerals, generate free radicals, which, in turn, may contribute to this type of injury. This study examined the characteristics of H2O2 production in a parenteral amino acid solution modelled on a commercially available paediatric parenteral amino acid solution. 2. The solution was exposed to light in the presence of riboflavin-5'-monophosphate (riboflavin), and peroxide formation in the presence and absence of catalase (H2O2 formation) was assayed using potassium iodide/molybdate. 3. Peak H2O2 production occurred at a light intensity of 8 microW cm-2 nm-1 in the 425-475 nm waveband and was linear to 2 h of light exposure. H2O2 production reached 500 mumol/l at 24 h. 4. H2O2 was directly related to a riboflavin concentration of up to 20 mumol/l and was maximal at 30 mumol/l. 5. H2O2 production was greatest in the amino acid/riboflavin solution at a pH of between 5 and 6. 6. Under the conditions of light exposure intensity, light exposure time, riboflavin concentration and pH found during the administration of parenteral nutrition in neonatal intensive care units, net H2O2 production occurs in solutions modelled on a paediatric parenteral amino acid preparation.

Tumor cell membrane-targeting pH-dependent electron donor-acceptor fluorescence systems with low background signals.

PubMed

Han, Liang; Liu, Mingming; Ye, Deyong; Zhang, Ning; Lim, Ed; Lu, Jing; Jiang, Chen

2014-03-01

Minimizing the background signal is crucial for developing tumor-imaging techniques with sufficient specificity and sensitivity. Here we use pH difference between healthy tissues and tumor and tumor targeting delivery to achieve this goal. We synthesize fluorophore-dopamine conjugate as pH-dependent electron donor-acceptor fluorescence system. Fluorophores are highly sensitive to electron-transfer processes, which can alter their optical properties. The intrinsic redox properties of dopamine are oxidation of hydroquinone to quinone at basic pH and reduction of quinone to hydroquinone at acidic pH. Quinone can accept electron then quench fluorescence. We design tumor cell membrane-targeting carrier for delivery. We demonstrate quenched fluorophore-quinone can be specially transferred to tumor extracellular environment and tumor-accumulated fluorophore can be activated by acidic pH. These tumor-targeting pH-dependent electron donor-acceptor fluorescence systems may offer new opportunity for developing tumor-imaging techniques. Copyright © 2014 Elsevier Ltd. All rights reserved.

Towards building artificial light harvesting complexes: enhanced singlet-singlet energy transfer between donor and acceptor pairs bound to albumins.

PubMed

Kumar, Challa V; Duff, Michael R

2008-12-01

Specific donor and acceptor pairs have been assembled in bovine serum albumin (BSA), at neutral pH and room temperature, and these dye-protein complexes indicated efficient donor to acceptor singlet-singlet energy transfer. For example, pyrene-1-butyric acid served as the donor and Coumarin 540A served as the acceptor. Both the donor and the acceptor bind to BSA with affinity constants in excess of 2x10(5) M(-1), as measured in absorption and circular dichroism (CD) spectral titrations. Simultaneous binding of both the donor and the acceptor chromophores was supported by CD spectra and one chromophore did not displace the other from the protein host, even when limited concentrations of the host were used. For example, a 1:1:1 complex between the donor, acceptor and the host can be readily formed, and spectral data clearly show that the binding sites are mutually exclusive. The ternary complexes (two different ligands bound to the same protein molecule) provided opportunities to examine singlet-singlet energy transfer between the protein-bound chromophores. Donor emission was quenched by the addition of the acceptor, in the presence of limited amounts of BSA, while no energy transfer was observed in the absence of the protein host, under the same conditions. The excitation spectra of the donor-acceptor-host complexes clearly show the sensitization of acceptor emission by the donor. Protein denaturation, as induced by the addition of urea or increasing the temperature to 360 K, inhibited energy transfer, which indicate that protein structure plays an important role. Sensitization also proceeded at low temperature (77 K) and diffusion of the donor or the acceptor is not required for energy transfer. Stern-Volmer quenching plots show that the quenching constant is (3.1+/-0.2)x10(4) M(-1), at low acceptor concentrations (<35 microM). Other albumins such as human and porcine proteins also served as good hosts for the above experiments. For the first time, non

Polymerization of beta-amino acids in aqueous solution

NASA Technical Reports Server (NTRS)

Liu, R.; Orgel, L. E.; Bada, J. L. (Principal Investigator)

1998-01-01

We have compared carbonyl diimidazole (CDI) and 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide (EDAC) as activating agents for the oligomerization of negatively-charged alpha- and beta-amino acids in homogeneous aqueous solution. alpha-Amino acids can be oligomerized efficiently using CDI, but not by EDAC. beta-Amino acids can be oligomerized efficiently using EDAC, but not by CDI. Aspartic acid, an alpha- and beta-dicarboxylic acid is oligomerized efficiently by both reagents. These results are explained in terms of the mechanisms of the reactions, and their relevance to prebiotic chemistry is discussed.

Hydrogen Bond Donor/Acceptor Cosolvent-Modified Choline Chloride-Based Deep Eutectic Solvents.

PubMed

Pandey, Ashish; Bhawna; Dhingra, Divya; Pandey, Siddharth

2017-04-27

Deep eutectic solvents (DESs) have emerged as nontoxic and inexpensive alternatives not only to the common organic solvents but to the ionic liquids as well. Some of the common and popular, and perhaps the most investigated, DESs are the ones comprising an ammonium salt and an appropriate hydrogen bond (HB) donor in a predetermined mole ratio. The formation of the DES is attributed to the H-bonding interaction(s) present between the salt and the HB donor. Consequently, addition of a predominantly HB donor or a predominantly HB acceptor cosolvent to such DESs may result in intriguing features and properties. We present investigation of two DESs constituted of salt choline chloride along with HB donors urea and glycerol, respectively, in 1:2 mol ratio, named reline and glyceline as the cosolvent of very high HB donating acidity and no HB accepting basicity 2,2,2-trifluoroethanol (TFE) and of very high HB accepting basicity and no HB donating acidity hexamethylphosphoramide (HMPA), respectively, is added. TFE shows up to 0.25 mole fraction miscibility with both reline and glyceline. While up to 0.25 mole fraction HMPA in glyceline results in transparent mixtures, this cosolvent is found to be completely immiscible with reline. From the perspective of the solvatochromic absorbance and fluorescence probes, it is established that the cybotactic region dipolarity within up to 0.25 mole fraction TFE/HMPA-added DES strongly depends on the functionalities present on the solute. Fourier transform infrared absorbance and Raman spectroscopic investigations reveal no major shifts in vibrational transitions as TFE/HMPA is added to the DES; spectral band broadening, albeit small, is observed nonetheless. Excess molar volumes and excess logarithmic viscosities of the mixtures indicate that while TFE may interstitially accommodate itself within H-bonded network of reline, it does appear to form H-bonds with the constituents of the glyceline. Increase in overall net repulsive

Molecular dynamics study on glycolic acid in the physiological salt solution

NASA Astrophysics Data System (ADS)

Matsunaga, S.

2018-05-01

Molecular dynamics (MD) study on glycolic acid in the physiological salt solution has been performed, which is a model of a biofuel cell. The structure and charge distribution of glycolic acid in aqueous solution used in MD is beforehand optimized by Gaussian09 utilizing the density functional theory. MD is performed in the NTV constant condition, i.e. the number of particles, temperature, and volume of MD cell are definite. The structure difference of the glycolic acid and oxalic acid is detected by the water distribution around the molecules using the pair distribution functions, gij(r), and the frequency dependent diffusion coefficients, Di(ν). The anomalous dielectric constant of the solution, i.e. about 12 times larger than that of water, has been obtained, which may be attributed to the ion pair formation in the solution.

Mechanisms of neptunium redox reactions in nitric acid solutions

DOE Office of Scientific and Technical Information (OSTI.GOV)

Chatterjee, Sayandev; Bryan, Samuel A.; Casella, Amanda J.

First transuranium element neptunium (Np) exhibits complicated behavior in acidic solutions because it can adopt wide range of oxidation states typically from +3 to +6 and coordinate large variety of ligands. In particular, accurate determination of Np redox potentials in nitric acid solutions is challenging due to overlapping chemical and electrochemical reactions leading to significant experimental uncertainties. Furthermore, over past decades spectrophotometry has been extensively applied to identify and characterize Np solution species in different oxidation states. However, relevant spectral database of Np in nitric acid solutions that can serve for the reference purposes has yet to be established duemore » to the experimental difficulty to isolate and stabilize Np species in pure oxidation states without compromising solution optical properties. This work demonstrates that combination of voltammetry and controlled-potential in situ thin-layer spectropotentiometry overcomes these challenges so that Np species in pure +3, +4, +5, or +6 oxidation states were electrochemically generated in the systematically varied 0.1 – 5 M nitric acid solutions, and corresponding vis-NIR spectral signatures were obtained. In situ optical monitoring of the interconversion between adjacent Np oxidation states resulted in elucidation of the mechanisms of the involved redox reactions, in-depth understanding of the relative stability of the Np oxidation states, and allowed benchmarking of the redox potentials of the NpO22+/NpO2+, NpO2+/Np4+ and Np4+/Np3+ couples. Notably, the NpO2+/Np4+ couple was distinguished from the proximal Np4+/Np3+ process overcoming previous concerns and challenges encountered in accurate determination of the respective potentials.« less

The Dependence of Donor:Acceptor Ratio on the Photovoltaic Performances of Blended poly (3-octylthiophene-2,5-diyl) and (6,6)-phenyl C{sub 71} butyric acid methyl ester Bulk Heterojunction Organic Solar Cells

DOE Office of Scientific and Technical Information (OSTI.GOV)

Fauzia, Vivi; Institute of Microengineering and Nanoelectronics; Umar, Akrajas Ali

2010-10-24

Bulk heterojunction organic solar cells using blended poly (3-octylthiophene-2,5-diyl)(P3OT) and (6,6)-phenyl C{sub 71} butyric acid methyl ester (PC{sub 71}BM) have been fabricated. P3OT and PC{sub 71}BM were used as the electron donor (D) and acceptor (A), respectively. Both materials were mixed and dissolved in dichlorobenzene with three different D:A ratios i.e. 1:3, 1:1 and 3:1 (weight) while maintained at the concentration of 2 wt%(26 mg/ml). The blended thin films were sandwiched between the indium tin oxide (ITO) coated glass and the aluminum film. This paper reports the influence of donor:acceptor ratio on the performance of solar cell devices measured bymore » current-voltage measurement both in the dark and under 1.5 AM solar illumination. It was found that all devices showed the photovoltaic effect with poor diode behavior and the donor:acceptor ratio significantly influenced on the performance of bulk heterojunction organic solar cells.« less

J-V and C-V investigation of the effect of small molecular fullerene and non-fullerene acceptors for CH3NH3PbI3 perovskite solar cell

NASA Astrophysics Data System (ADS)

Zheng, Yanqiong; Wang, Chao; Yu, Junle; Yang, Fang; Zhang, Jing; Wei, Bin; Li, Weishi

2017-11-01

To find the ideal acceptors for perovskite solar cells (PSCs) and get insight into the dielectric property at the interface between perovskite and acceptor, series of small molecular fullerene and non-fullerene acceptors were comparatively investigated. Fullerene acceptors based PSCs show higher performance than non-fullerene acceptors based PSCs. However, the perylene tetracarboxylic diimide based PSC has achieved a η PCE of 4.70%, implying that it is a promising acceptor candidate for PSCs because of its suitable energy level, high electron mobility, and smooth surface. By employing double acceptors of (6,6)-phenyl-C61-butyric acid methyl ester (PCBM)/C60 or PCBM/3,4,9,10-perylenetetracarboxylic bisbenzimidazole, the PSC stability is greatly improved even without performance enhancement. The perovskite (Pero)/PCBM film shows smooth surface, suggesting that PCBM penetrates into the Pero layer. The hydrophobicity trend of Pero/acceptor composite films is same as the device performance by judging from the water contact angle, and Pero/PCBM as well as Pero/C60 show higher hydrophobicity than other Pero/small-molecular-acceptor composite films. Capacitance-voltage characteristics of the series of single and double acceptor based PSCs were measured. The double acceptor based PSCs show larger depletion layer width (W d) than single acceptor based PSCs. Meanwhile, the defect density (N A) in Pero layer for single acceptor based PSCs is larger than that for double acceptor based PSCs, implying better n-doping of Pero layer by using a single acceptor.

An Overview of Electron Acceptors in Microbial Fuel Cells

PubMed Central

Ucar, Deniz; Zhang, Yifeng; Angelidaki, Irini

2017-01-01

Microbial fuel cells (MFC) have recently received increasing attention due to their promising potential in sustainable wastewater treatment and contaminant removal. In general, contaminants can be removed either as an electron donor via microbial catalyzed oxidization at the anode or removed at the cathode as electron acceptors through reduction. Some contaminants can also function as electron mediators at the anode or cathode. While previous studies have done a thorough assessment of electron donors, cathodic electron acceptors and mediators have not been as well described. Oxygen is widely used as an electron acceptor due to its high oxidation potential and ready availability. Recent studies, however, have begun to assess the use of different electron acceptors because of the (1) diversity of redox potential, (2) needs of alternative and more efficient cathode reaction, and (3) expanding of MFC based technologies in different areas. The aim of this review was to evaluate the performance and applicability of various electron acceptors and mediators used in MFCs. This review also evaluated the corresponding performance, advantages and disadvantages, and future potential applications of select electron acceptors (e.g., nitrate, iron, copper, perchlorate) and mediators. PMID:28469607

Rise-Time of FRET-Acceptor Fluorescence Tracks Protein Folding

PubMed Central

Lindhoud, Simon; Westphal, Adrie H.; van Mierlo, Carlo P. M.; Visser, Antonie J. W. G.; Borst, Jan Willem

2014-01-01

Uniform labeling of proteins with fluorescent donor and acceptor dyes with an equimolar ratio is paramount for accurate determination of Förster resonance energy transfer (FRET) efficiencies. In practice, however, the labeled protein population contains donor-labeled molecules that have no corresponding acceptor. These FRET-inactive donors contaminate the donor fluorescence signal, which leads to underestimation of FRET efficiencies in conventional fluorescence intensity and lifetime-based FRET experiments. Such contamination is avoided if FRET efficiencies are extracted from the rise time of acceptor fluorescence upon donor excitation. The reciprocal value of the rise time of acceptor fluorescence is equal to the decay rate of the FRET-active donor fluorescence. Here, we have determined rise times of sensitized acceptor fluorescence to study the folding of double-labeled apoflavodoxin molecules and show that this approach tracks the characteristics of apoflavodoxinʼs complex folding pathway. PMID:25535076

Kinetic modeling of a bi-enzymatic system for efficient conversion of lactose to lactobionic acid.

PubMed

Van Hecke, Wouter; Bhagwat, Aditya; Ludwig, Roland; Dewulf, Jo; Haltrich, Dietmar; Van Langenhove, Herman

2009-04-01

A model has been developed to describe the interaction between two enzymes and an intermediary redox mediator. In this bi-enzymatic process, the enzyme cellobiose dehydrogenase oxidizes lactose at the C-1 position of the reducing sugar moiety to lactobionolactone, which spontaneously hydrolyzes to lactobionic acid. 2,2'-Azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) diammonium salt is used as electron acceptor and is continuously regenerated by laccase. Oxygen is the terminal electron acceptor and is fully reduced to water by laccase, a copper-containing oxidase. Oxygen is added to the system by means of bubble-free oxygenation. Using the model, the productivity of the process is investigated by simultaneous solution of the rate equations for varying enzyme quantities and redox mediator concentrations, solved with the aid of a numerical solution. The isocharts developed in this work provide an easy-to-use graphical tool to determine optimal process conditions. The model allows the optimization of the employed activities of the two enzymes and the redox mediator concentration for a given overall oxygen mass transfer coefficient by using the isocharts. Model predictions are well in agreement with the experimental data.

A study of acceptors and non-acceptors of family planning methods among three tribal communities.

PubMed

Mutharayappa, R

1995-03-01

Primary data were collected from 399 currently married women of the Marati, Malekudiya, and Koraga tribes in the Dakshina Kannada district of Karnataka State in this study of the implementation of family planning programs in tribal areas. The Marati, Malekudiya, and Koraga tribes are three different endogamous tribal populations living in similar ecological conditions. Higher levels of literacy and a high rate of acceptance of family planning methods, however, have been observed among these tribes compared to the rest of the tribal population in the state. 46.4% of currently married women aged 15-49 years in the tribes were acceptors of family planning methods, having a mean 3.7 children. The majority of acceptors opted for tubectomy and vasectomy. The adoption of spacing methods is less common among tribal people. Most acceptors received their operations through government health facilities. They were motivated mainly by female health workers and received both cash and other incentives to accept family planning. The main reason for non-acceptance of family planning among non-acceptors was the desire to conceive and bear more children. The data indicate that most of the tribal households are nuclear families with household size more or less similar to that of the general population. They have a higher literacy rate than the rest of the tribal population in the state, with literacy levels between males and females and between the three tribes being quite different; the school enrollment ratio is relatively higher for both boys and girls.

Salicylic acid peels versus Jessner's solution for acne vulgaris: a comparative study.

PubMed

Bae, Byung Gi; Park, Chang Ook; Shin, Hyoseung; Lee, Soo Hyun; Lee, Yun Sun; Lee, Sang Ju; Chung, Kee Yang; Lee, Kwang Hoon; Lee, Ju Hee

2013-02-01

Salicylic acid was recently formulated in a hydroethanolic vehicle at a concentration of 20% to 30%. Salicylic acid has strong comedolytic effects because of its lipophilic nature. To compare the therapeutic efficacy and tolerability of salicylic acid peels with those of Jessner's solution peels in patients with acne vulgaris. Thirteen patients (13 men; mean age 22.6, range 20-28) with facial acne were enrolled. Jessner's solution was applied to one side of each patient's face and 30% salicylic acid to the other in three sessions at 2-week intervals. A blinded investigator counted noninflammatory and inflammatory lesions before treatment and 2 weeks after each treatment. Inflammatory and noninflammatory acne lesion counts decreased in proportion to the duration of treatment. Inflammatory acne lesion counts did not differ significantly between salicylic acid and Jessner's solution peels, although in terms of noninflammatory acne lesion counts, sites treated with salicylic acid showed significant improvement (p = .04), whereas those treated with Jessner's solution did not. We found that 30% salicylic acid peels were effective for inflammatory acne and more effective than Jessner's solution peels for treating noninflammatory acne. © 2012 by the American Society for Dermatologic Surgery, Inc. Published by Wiley Periodicals, Inc.

Method for producing and regenerating a synthetic CO.sub.2 acceptor

DOEpatents

Lancet, Michael S [Pittsburgh, PA; Curran, George P [Pittsburgh, PA; Gorin, Everett [San Rafael, CA

1982-01-01

A method for producing a synthetic CO.sub.2 acceptor by feeding a mixture of finely divided silica and at least one finely divided calcium compound selected from the group consisting of calcium oxide and calcium carbonate to a fluidized bed; operating the fluidized bed at suitable conditions to produce pellets of synthetic CO.sub.2 acceptor and recovering the pellets of synthetic CO.sub.2 acceptor from the fluidized bed. Optionally, spent synthetic CO.sub.2 acceptor can be charged to the fluidized bed to produce regenerated pellets of synthetic CO.sub.2 acceptor.

Asymmetric intramolecular α-cyclopropanation of aldehydes using a donor/acceptor carbene mimetic

PubMed Central

Luo, Chaosheng; Wang, Zhen; Huang, Yong

2015-01-01

Enantioselective α-alkylation of carbonyl is considered as one of the most important processes for asymmetric synthesis. Common alkylation agents, that is, alkyl halides, are notorious substrates for both Lewis acids and organocatalysts. Recently, olefins emerged as a benign alkylating species via photo/radical mechanisms. However, examples of enantioselective alkylation of aldehydes/ketones are scarce and direct asymmetric dialkylation remains elusive. Here we report an intramolecular α-cyclopropanation reaction of olefinic aldehydes to form chiral cyclopropane aldehydes. We demonstrate that an α-iodo aldehyde can function as a donor/acceptor carbene equivalent, which engages in a formal [2+1] annulation with a tethered double bond. Privileged bicyclo[3.1.0]hexane-type scaffolds are prepared in good optical purity using a chiral amine. The synthetic utility of the products is demonstrated by versatile transformations of the bridgehead formyl functionality. We expect the concept of using α-iodo iminium as a donor/acceptor carbene surrogate will find wide applications in chemical reaction development. PMID:26644194

Assessment of a New Type of Coin Acceptor

DOT National Transportation Integrated Search

1983-04-01

An assessment of the Mars Money Systems Model CD 540-1 coin acceptor associated with farecard vendors was conducted at the Port Authority Transit Corp. as part of an appraisal of automatic fare collection (AFC) equipment. The Mars acceptor consistent...

Surface tensions of solutions containing dicarboxylic acid mixtures

NASA Astrophysics Data System (ADS)

Lee, Jae Young; Hildemann, Lynn M.

2014-06-01

Organic solutes tend to lower the surface tension of cloud condensation nuclei, allowing them to more readily activate. The surface tension of various dicarboxylic acid aerosol mixtures was measured at 20 °C using the Wilhelmy plate method. At lower concentrations, the surface tension of a solution with equi-molar mixtures of dicarboxylic acids closely followed that of a solution with the most surface-active organic component alone. Measurements of surface tension for these mixtures were lower than predictions using Henning's model and the modified Szyszkowski equation, by ˜1-2%. The calculated maximum surface excess (Γmax) and inverse Langmuir adsorption coefficient (β) from the modified Szyszkowski equation were both larger than measured values for 6 of the 7 mixtures tested. Accounting for the reduction in surface tension in the Köhler equation reduced the critical saturation ratio for these multi-component mixtures - changes were negligible for dry diameters of 0.1 and 0.5 μm, but a reduction from 1.0068 to 1.0063 was seen for the 4-dicarboxylic acid mixture with a dry diameter of 0.05 μm.

Acid-base equilibrium in aqueous solutions of 1,3-dimethylbarbituric acid as studied by 13C NMR spectroscopy

NASA Astrophysics Data System (ADS)

Gryff-Keller, A.; Kraska-Dziadecka, A.

2011-12-01

13C NMR spectra of 1,3-dimethylbarbituric acid in aqueous solutions of various acidities and for various solute concentrations have been recorded and interpreted. The spectra recorded at pH = 2 and below contain the signals of the neutral solute molecule exclusively, while the ones recorded at pH = 7 and above only the signals of the appropriate anion, which has been confirmed by theoretical GIAO-DFT calculations. The signals in the spectra recorded for solutions of pH < 7 show dynamic broadenings. The lineshape analysis of these signals has provided information on the kinetics of the processes running in the dynamic acid-base equilibrium. The kinetic data determined this way have been used to clarify the mechanisms of these processes. The numerical analysis has shown that under the investigated conditions deprotonation of the neutral solute molecules undergoes not only via a simple transfer of the C-H proton to water molecules but also through a process with participation of the barbiturate anions. Moreover, the importance of tautomerism, or association, or both these phenomena for the kinetics of the acid-base transformations in the investigated system has been shown. Qualitatively similar changes of 13C NMR spectra with the solution pH variation have been observed for the parent barbituric acid.

Alternansucrase acceptor reactions with D-tagatose and L-glucose.

PubMed

Côté, Gregory L; Dunlap, Christopher A; Appell, Michael; Momany, Frank A

2005-02-07

Alternansucrase (EC 2.4.1.140) is a d-glucansucrase that synthesizes an alternating alpha-(1-->3), (1-->6)-linked d-glucan from sucrose. It also synthesizes oligosaccharides via d-glucopyranosyl transfer to various acceptor sugars. Two of the more efficient monosaccharide acceptors are D-tagatose and L-glucose. In the presence of d-tagatose, alternansucrase produced the disaccharide alpha-d-glucopyranosyl-(1-->1)-beta-D-tagatopyranose via glucosyl transfer. This disaccharide is analogous to trehalulose. We were unable to isolate a disaccharide product from L-glucose, but the trisaccharide alpha-D-glucopyranosyl-(1-->6)-alpha-d-glucopyranosyl-(1-->4)-l-glucose was isolated and identified. This is analogous to panose, one of the structural units of pullulan, in which the reducing-end D-glucose residue has been replaced by its L-enantiomer. The putative L-glucose disaccharide product, produced by glucoamylase hydrolysis of the trisaccharide, was found to be an acceptor for alternansucrase. The disaccharide, alpha-D-glucopyranosyl-(1-->4)-L-glucose, was a better acceptor than maltose, previously the best known acceptor for alternansucrase. A structure comparison of alpha-D-glucopyranosyl-(1-->4)-L-glucose and maltose was performed through computer modeling to identify common features, which may be important in acceptor affinity by alternansucrase.

Method for producing and regenerating a synthetic CO[sub 2] acceptor

DOEpatents

Lancet, M. S.; Curran, G. P.; Gorin, E.

1982-05-18

A method is described for producing a synthetic CO[sub 2] acceptor by feeding a mixture of finely divided silica and at least one finely divided calcium compound selected from the group consisting of calcium oxide and calcium carbonate to a fluidized bed; operating the fluidized bed at suitable conditions to produce pellets of synthetic CO[sub 2] acceptor and recovering the pellets of synthetic CO[sub 2] acceptor from the fluidized bed. Optionally, spent synthetic CO[sub 2] acceptor can be charged to the fluidized bed to produce regenerated pellets of synthetic CO[sub 2] acceptor. 1 fig.

Method for incorporating radioactive phosphoric acid solutions in concrete

DOEpatents

Wolf, G.A.; Smith, J.W.; Ihle, N.C.

1982-07-08

A method for incorporating radioactive phosphoric acid solutions in concrete is described wherein the phosphoric acid is reacted with Ca(OH)/sub 2/ to form a precipitate of hydroxyapatite and the hydroxyapatite is mixed with Portland cement to form concrete.

Method for incorporating radioactive phosphoric acid solutions in concrete

DOEpatents

Wolf, Gary A [Kennewick, WA; Smith, Jeffrey W [Lancaster, OH; Ihle, Nathan C [Walla Walla, WA

1984-01-01

A method for incorporating radioactive phosphoric acid solutions in concrete is described wherein the phosphoric acid is reacted with Ca(OH).sub.2 to form a precipitate of hydroxyapatite and the hydroxyapatite is mixed with portland cement to form concrete.

Mapping the Relationship between Glycosyl Acceptor Reactivity and Glycosylation Stereoselectivity.

PubMed

van der Vorm, Stefan; van Hengst, Jacob M A; Bakker, Marloes; Overkleeft, Herman S; van der Marel, Gijsbert A; Codée, Jeroen D C

2018-03-30

The reactivity of both coupling partners-the glycosyl donor and acceptor-is decisive for the outcome of a glycosylation reaction, in terms of both yield and stereoselectivity. Where the reactivity of glycosyl donors is well understood and can be controlled through manipulation of the functional/protecting-group pattern, the reactivity of glycosyl acceptor alcohols is poorly understood. We here present an operationally simple system to gauge glycosyl acceptor reactivity, which employs two conformationally locked donors with stereoselectivity that critically depends on the reactivity of the nucleophile. A wide array of acceptors was screened and their structure-reactivity/stereoselectivity relationships established. By systematically varying the protecting groups, the reactivity of glycosyl acceptors can be adjusted to attain stereoselective cis-glucosylations. © 2018 The Authors. Published by Wiley-VCH Verlag GmbH & Co. KGaA.

Defining donor and acceptor strength in conjugated copolymers

NASA Astrophysics Data System (ADS)

Hedström, Svante; Wang, Ergang; Persson, Petter

2017-03-01

The progress in efficiency of organic photovoltaic devices is largely driven by the development of new donor-acceptor (D-A) copolymers. The number of possible D-A combinations escalates rapidly with the ever-increasing number of donor and acceptor units, and the design process often involves a trial-and-error approach. We here present a computationally efficient methodology for the prediction of optical and electronic properties of D-A copolymers based on density functional theory calculations of donor- and acceptor-only homopolymers. Ten donors and eight acceptors are studied, as well as all of their 80 D-A copolymer combinations, showing absorption energies of 1.3-2.3 eV, and absorption strengths varying by up to a factor of 2.5. Focus lies on exhibited trends in frontier orbital energies, optical band gaps, and absorption intensities, as well as their relation to the molecular structure. Based on the results, we define the concept of donor and acceptor strength, and calculate this quantity for all investigated units. The light-harvesting capabilities of the 80 D-A copolymers were also assessed. This gives a valuable theoretical guideline to the design of D-A copolymers with the potential to reduce the synthesis efforts in the development of new polymers.

Methanol Uptake by Low Temperature Aqueous Sulfuric Acid Solutions

NASA Technical Reports Server (NTRS)

Iraci, L. T.; Essin, A. M.; Golden, D. M.; Hipskind, R. Stephen (Technical Monitor)

2001-01-01

The global methanol budget is currently unbalanced, with source terms significantly larger than the sinks terms. To evaluate possible losses of gaseous methanol to sulfate aerosols, the solubility and reactivity of methanol in aqueous sulfuric acid solutions representative of upper tropospheric and lower stratospheric aerosols is under investigation. Methanol will partition into sulfate aerosols according to its Henry's law solubility. Using standard uptake techniques in a Knudsen cell reactor, we have measured the effective Henry's law coefficient, H*, for cold (196 - 220 K) solutions ranging between 45 and 70 wt % H2SO4. We have found that methanol solubility ranges from approx. 10(exp 5) - 10(exp 7) M/atm for UT/LS conditions. Solubility increases with decreasing temperature and with increasing sulfuric acid content. Although methanol is slightly more soluble than are acetone and formaldehyde, current data indicate that uptake by clean aqueous sulfuric acid particles will not be a significant sink for methanol in the UT/LS. These solubility measurements include uptake due to physical solvation and any rapid equilibria which are established in solution. Reaction between primary alcohols and sulfuric acid does occur, leading to the production of alkyl sulfates. Literature values for the rate of this reaction suggest that formation of CH3OSO3H is not significant over our experimental time scale for solutions below 80 wt % H2SO4. To confirm this directly, results obtained using a complementary equilibrium measurement technique will also be presented.

Nanographenes as electron-deficient cores of donor-acceptor systems.

PubMed

Liu, Yu-Min; Hou, Hao; Zhou, Yan-Zhen; Zhao, Xin-Jing; Tang, Chun; Tan, Yuan-Zhi; Müllen, Klaus

2018-05-15

Conjugation of nanographenes (NGs) with electro-active molecules can establish donor-acceptor π-systems in which the former generally serve as the electron-donating moieties due to their electronic-rich nature. In contrast, here we report a series of reversed donor-acceptor structures are obtained by C-N coupling of electron-deficient perchlorinated NGs with electron-rich anilines. Selective amination at the vertexes of the NGs is unambiguously shown through X-ray crystallography. By varying the donating ability of the anilino groups, the optical and assembly properties of donor-acceptor NGs can be finely modulated. The electron-deficient concave core of the resulting conjugates can host electron-rich guest molecules by intermolecular donor-acceptor interactions and gives rise to charge-transfer supramolecular architectures.

Reprocessing system with nuclide separation based on chromatography in hydrochloric acid solution

DOE Office of Scientific and Technical Information (OSTI.GOV)

Suzuki, Tatsuya; Tachibana, Yu; Koyama, Shi-ichi

2013-07-01

We have proposed the reprocessing system with nuclide separation processes based on the chromatographic technique in the hydrochloric acid solution system. Our proposed system consists of the dissolution process, the reprocessing process, the minor actinide separation process, and nuclide separation processes. In the reprocessing and separation processes, the pyridine resin is used as a main separation media. It was confirmed that the dissolution in the hydrochloric acid solution is easily achieved by the plasma voloxidation and by the addition of oxygen peroxide into the hydrochloric acid solution.

Phosphorylation of Glyceric Acid in Aqueous Solution Using Trimetaphosphate

NASA Technical Reports Server (NTRS)

Kolb, Vera; Orgel, Leslie E.

1996-01-01

The phosphorylation of glyceric acid is an interesting prebiotic reaction because it converts a simple, potentially prebiotic organic molecule into phosphate derivatives that are central to carbohydrate metabolism. We find that 0.05 M glyceric acid in the presence of 0.5 M trimetaphosphate in alkaline solution gives a mixture of 2- and 3-phosphoglyceric acids in combined yields of up to 40%.

Ionizing radiation induced degradation of salicylic acid in aqueous solution

NASA Astrophysics Data System (ADS)

Albarrán, Guadalupe; Mendoza, Edith

2018-06-01

The radiation-induced degradation of salicylic acid (SA-) in aqueous solutions (1.0 and 0.1 mmol dm-3) saturated with N2O or air or without oxygen were studied. Irradiation was carried out using a cobalt-60 source. With a 1 mmol dm-3 solution saturated with N2O a seemingly total degradation occurred at about 18 kGy, although small quantities of 2,3-dihydroxybenzoic acid, catechol and 2,5-dihydroxybenzoic acid were present at that dose at concentrations of 67, 22 and 6 μmol dm-3 respectively. Under air and when free oxygen, the three radiolytic products were present at 18.54 kGy while SA- was destroyed only to 90% and 62%, respectively. In the case of 0.1 mmol dm-3 SA- solutions, the acid was degraded at 3.5 kGy if the solution contained N2O, at 5.8 kGy in air and at 7 kGy without oxygen. The concentration of the radiolytic products increased with increasing dose and after a maximum they decreased. The oxidation was followed by measuring the chemical oxygen demand; the slopes were 0.48 and 0.11, 0.21 and 0.07, 0.15 and 0.03 mmol dm-3 kGy-1 for 1.0 and 0.10 mmol dm-3 solutions saturated with N2O or air or without oxygen, respectively.

RECOVERY OF ACTINIDES FROM AQUEOUS NITRIC ACID SOLUTIONS

DOEpatents

Ader, M.

1963-11-19

A process of recovering actinides is presented. Tetravalent actinides are extracted from rare earths in an aqueous nitric acid solution with a ketone and back-extracted from the ketone into an aqueous medium. The aqueous actinide solution thus obtained, prior to concentration by boiling, is sparged with steam to reduce its ketone to a maximum content of 3 grams per liter. (AEC)

Morphological study on small molecule acceptor-based organic solar cells with efficiencies beyond 7% (Presentation Recording)

NASA Astrophysics Data System (ADS)

Ma, Wei; Yan, He

2015-10-01

Despite the essential role of fullerenes in achieving best-performance organic solar cells (OSCs), fullerene acceptors have several drawbacks including poor light absorption, high-cost production and purification. For this reason, small molecule acceptor (SMA)-based OSCs have attracted much attention due to the easy tunability of electronic and optical properties of SMA materials. In this study, polymers with temperature dependent aggregation behaviors are combined with various small molecule acceptor materials, which lead to impressive power conversion efficiencies of up to 7.3%. The morphological and aggregation properties of the polymer:small molecule blends are studied in details. It is found that the temperature-dependent aggregation behavior of polymers allows for the processing of the polymer solutions at moderately elevated temperature, and more importantly, controlled aggregation and strong crystallization of the polymer during the film cooling and drying process. This results in a well-controlled and near-ideal polymer:small molecule morphology that is controlled by polymer aggregation during warm casting and thus insensitive to the choice of small molecules. As a result, several cases of highly efficient (PCE between 6-7.3%) SMA OSCs are achieved. The second part of this presentation will describe the morphology of a new small molecule acceptor with a unique 3D structure. The relationship between molecular structure and morphology is revealed.

Interaction between Al3+ and acrylic acid and polyacrylic acid in acidic aqueous solution: a model experiment for the behavior of Al3+ in acidified soil solution.

PubMed

Etou, Mayumi; Masaki, Yuka; Tsuji, Yutaka; Saito, Tomoyuki; Bai, Shuqin; Nishida, Ikuko; Okaue, Yoshihiro; Yokoyama, Takushi

2011-01-01

From the viewpoint of the phytotoxicity and mobility of Al(3+) released from soil minerals due to soil acidification, the interaction between Al(3+) and acrylic acid (AA) and polyacrylic acid (PAA) as a model compound of fulvic acid was investigated. The interaction was examined at pH 3 so as to avoid the hydrolysis of Al(3+). The interaction between Al(3+) and AA was weak. However, the interaction between Al(3+) and PAA was strong and depended on the initial (COOH in PAA)/Al molar ratio (R(P)) of the solution. For the range of 1/R(P), the interaction between Al(3+) and PAA can be divided into three categories: (1) 1:1 Al-PAA-complex (an Al(3+) combines to a carboxyl group), (2) intermolecular Al-PAA-complex (an Al(3+) combines to more than 2 carboxyl groups of other Al-PAA-complexes) in addition to the 1:1 Al-PAA-complex and (3) precipitation of intermolecular complexes. In conclusion, R(P) is an important factor affecting the behavior of Al(3+) in acidic soil solution.

IN VITRO INTERACTIONS BETWEEN LACTIC ACID SOLUTION AND ART GLASS-IONOMER CEMENTS

PubMed Central

Wang, Linda; Cefaly, Daniela Francisca Gigo; dos Santos, Janaína Lima; dos Santos, Jean Rodrigo; Lauris, José Roberto Pereira; Mondelli, Rafael Francisco Lia; Atta, Maria Teresa

2009-01-01

Objectives: Production of acids such as lactic acid contributes to establish a cariogenic environment that leads to dental substrate demineralization. Fluoride plays an important role in this case and, as fluoride-releasing materials, glass-ionomer cements are expected to contribute to minimize deleterious reactions. This study evaluated interactions of glass-ionomer cements used in atraumatic restorative treatment (ART-GICs) with an aqueous lactic acid solution, testing the null hypotheses that no changes occur in the pH of the solution or on the surface roughness and mass of the ART-GICs when exposed to lactic acid solution over a 6-week period. Material and Methods: Ketac Molar, Fuji IX, Vitro Molar and Magic Glass were tested, and compared to Filtek Z250 and Ketac Fil Plus as control groups. Six specimens of each material were made according to manufacturers' instructions. The pH of the solution and roughness and mass changes of each specimen were determined over 6 weeks. Each specimen was individually stored in 2 mL of 0.02 M lactic acid solution for 1 week, renewing the solution every week. pH of solution and mass of the specimens were monitored weekly, and surface roughness of the specimens was assessed before and at the end of the 6-week acid challenge. pH and mass data were analyzed statistically by repeated measures using one-way ANOVA and Tukey's post-hoc tests for each material. Paired t-tests were used for roughness analysis. Tukey's post-hoc tests were applied to verify differences of final roughness among the materials. Significance level was set at 5%. Results: The null hypotheses were partially rejected. All materials were able to increase the pH of the lactic acid solution and presented rougher surfaces after immersion, while mass change was minimal and generally not statistically significant. Conclusions: These findings can be helpful to predict the performance of these materials under clinical conditions. A protective action against the carious

Impact of Thermal Annealing on Organic Photovoltaic Cells Using Regioisomeric Donor-Acceptor-Acceptor Molecules.

PubMed

Zhang, Tao; Han, Han; Zou, Yunlong; Lee, Ying-Chi; Oshima, Hiroya; Wong, Ken-Tsung; Holmes, Russell J

2017-08-02

We report a promising set of donor-acceptor-acceptor (D-A-A) electron-donor materials based on coplanar thieno[3,2-b]/[2,3-b]indole, benzo[c][1,2,5]thiadiazole, and dicyanovinylene, which are found to show broadband absorption with high extinction coefficients. The role of the regioisomeric electron-donating thienoindole moiety on the physical and structural properties is examined. Bulk heterojunction (BHJ) organic photovoltaic cells (OPVs) based on the thieno[2,3-b]indole-based electron donor NTU-2, using C 70 as an electron acceptor, show a champion power conversion efficiency of 5.2% under AM 1.5G solar simulated illumination. This efficiency is limited by a low fill factor (FF), as has previously been the case in D-A-A systems. In order to identify the origin of the limited FF, further insight into donor layer charge-transport behavior is realized by examining planar heterojunction OPVs, with emphasis on the evolution of film morphology with thermal annealing. Compared to as-deposited OPVs that exhibit insufficient donor crystallinity, crystalline OPVs based on annealed thin films show an increase in the short-circuit current density, FF, and power conversion efficiency. These results suggest that that the crystallization of D-A-A molecules might not be realized spontaneously at room temperature and that further processing is needed to realize efficient charge transport in these materials.

Satisfied IUD acceptors as family planning motivators in Sri Lanka.

PubMed

Fisher, A A; de Silva, V

1986-01-01

In this study, government midwives were teamed with currently satisfied IUD acceptors to strengthen field motivational and recruitment efforts. The objective was to increase the number of new IUD acceptors. In the experimental study areas, a total of 3,019 new IUD acceptors were recruited. Time series regression analysis revealed a significant difference between the experimental and comparison areas that was over and above what might be expected on the basis of the past history of differences between these two areas. These and other findings suggest that teaming currently satisfied acceptors with government field-workers can have a substantial impact on the recruitment of new family planning users.

Distinctive acceptor-end structure and other determinants of Escherichia coli tRNAPro identity.

PubMed Central

McClain, W H; Schneider, J; Gabriel, K

1994-01-01

The previously uncharacterized determinants of the specificity of tRNAPro for aminoacylation (tRNAPro identity) were defined by a computer comparison of all Escherichia coli tRNA sequences and tested by a functional analysis of amber suppressor tRNAs in vivo. We determined the amino acid specificity of tRNA by sequencing a suppressed protein and the aminoacylation efficiency of tRNA by examining the steady-state level of aminoacyl-tRNA. On substituting nucleotides derived from the acceptor end and variable pocket of tRNAPro for the corresponding nucleotides in a tRNAPhe gene, the identity of the resulting tRNA changed substantially but incompletely to that of tRNAPro. The redesigned tRNAPhe was weakly active and aminoacyl-tRNA was not detected. Ethyl methanesulfonate mutagenesis of the redesigned tRNAPhe gene produced a mutant with a wobble pair in place of a base pair in the end of the acceptor-stem helix of the transcribed tRNA. This mutant exhibited both a tRNAPro identity and substantial aminoacyl-tRNA. The results speak for the importance of a distinctive conformation in the acceptor-stem helix of tRNAPro for aminoacylation by the prolyl-tRNA synthetase. The anticodon also contributes to tRNAPro identity but is not necessary in vivo. Images PMID:8127693

Treatment of infectious skin defects or ulcers with electrolyzed strong acid aqueous solution.

PubMed

Sekiya, S; Ohmori, K; Harii, K

1997-01-01

A chronic ulcer with an infection such as methicillin-resistant Staphylococcus aureus is hard to heal. Plastic and reconstructive surgeons often encounter such chronic ulcers that are resistant to surgical or various conservative treatments. We applied conservative treatment using an electrolyzed strong acid aqueous solution and obtained satisfactory results. The lesion was washed with the solution or soaked in a bowl of the solution for approximately 20 min twice a day. Fresh electrolyzed strong acid aqueous solution is unstable and should be stored in a cool, dark site in a sealed bottle. It should be used within a week after it has been produced. Here we report on 15 cases of infectious ulcers that were treated by electrolyzed strong acid aqueous solution. Of these cases, 7 patients were healed, 3 were granulated, and in 5, infection subsided. In most cases the lesion became less reddish and less edematous. Discharge or foul odor from the lesion was decreased. Electrolyzed strong acid aqueous solution was especially effective for treating a chronic refractory ulcer combined with diabetes melitus or peripheral circulatory insufficiency. This clinically applied therapy of electrolyzed strong acid aqueous solution was found to be effective so that this new therapeutic technique for ulcer treatment can now be conveniently utilized.

Influence of acceptor on charge mobility in stacked π-conjugated polymers

NASA Astrophysics Data System (ADS)

Sun, Shih-Jye; Menšík, Miroslav; Toman, Petr; Gagliardi, Alessio; Král, Karel

2018-02-01

We present a quantum molecular model to calculate mobility of π-stacked P3HT polymer layers with electron acceptor dopants coupled next to side groups in random position with respect to the linear chain. The hole density, the acceptor LUMO energy and the hybridization transfer integral between the acceptor and polymer were found to be very critical factors to the final hole mobility. For a dopant LUMO energy close and high above the top of the polymer valence band we have found a significant mobility increase with the hole concentration and with the dopant LUMO energy approaching the top of the polymer valence band. Higher mobility was achieved for small values of hybridization transfer integral between polymer and the acceptor, corresponding to the case of weakly bound acceptor. Strong couplings between the polymer and the acceptor with Coulomb repulsion interactions induced from the electron localizations was found to suppress the hole mobility.

Growth behavior of anodic porous alumina formed in malic acid solution

NASA Astrophysics Data System (ADS)

Kikuchi, Tatsuya; Yamamoto, Tsuyoshi; Suzuki, Ryosuke O.

2013-11-01

The growth behavior of anodic porous alumina formed on aluminum by anodizing in malic acid solutions was investigated. High-purity aluminum plates were electropolished in CH3COOH/HClO4 solutions and then anodized in 0.5 M malic acid solutions at 293 K and constant cell voltages of 200-350 V. The anodic porous alumina grew on the aluminum substrate at voltages of 200-250 V, and a black, burned oxide film was formed at higher voltages. The nanopores of the anodic oxide were only formed at grain boundaries of the aluminum substrate during the initial stage of anodizing, and then the growth region extended to the entire aluminum surface as the anodizing time increased. The anodic porous alumina with several defects was formed by anodizing in malic acid solution at 250 V, and oxide cells were approximately 300-800 nm in diameter.

Diketopyrrolopyrrole-based π-bridged donor-acceptor polymer for photovoltaic applications.

PubMed

Li, Wenting; Lee, Taegweon; Oh, Soong Ju; Kagan, Cherie R

2011-10-01

We report the synthesis, properties, and photovoltaic applications of a new conjugated copolymer (C12DPP-π-BT) containing a donor group (bithiophene) and an acceptor group (2,5-didodecylpyrrolo[3,4-c]pyrrole-1,4(2H,5H)-dione), bridged by a phenyl group. Using cyclic voltammetry, we found the energy levels of C12DPP-π-BT are intermediate to common electron donor and acceptor photovoltaic materials, poly (3-hexylthiophene-2,5-diyl) (P3HT) and [6,6]-phenyl-C61-butyric acid methyl ester (PCBM), respectively. Whereas P3HT and PCBM are exclusively electron donating or accepting, we predict C12DPP-π-BT may uniquely serve as either an electron donor or an acceptor when paired with PCBM or P3HT forming junctions with large built-in potentials. We confirmed the ambipolar nature of C12DPP-π-BT in space charge limited current measurements and in C12DPP-π-BT:PCBM and C12DPP-π-BT:P3HT bulk heterojunction solar cells, achieving power conversion efficiencies of 1.67% and 0.84%, respectively, under illumination of AM 1.5G (100 mW/cm(2)). Adding diiodooctane to C12DPP-π-BT:PCBM improved donor-acceptor inter-mixing and film uniformity, and therefore enhanced charge separation and overall device efficiency. Using higher-molecular-weight polymer C12DPP-π-BT in both C12DPP-π-BT:PCBM and C12DPP-π-BT:P3HT devices improved charge transport and hence the performance of the solar cells. In addition, we compared the structural and electronic properties of C12DPP-π-BT:PCBM and C12DPP-π-BT:P3HT blends, representing the materials classes of polymer:fullerene and polymer:polymer blends. In C12DPP-π-BT:PCBM blends, higher short circuit currents were obtained, consistent with faster charge transfer and balanced electron and hole transport, but lower open circuit voltages may be reduced by trap-assisted recombination and interfacial recombination losses. In contrast, C12DPP-π-BT:P3HT blends exhibit higher open circuit voltage, but short circuit currents were limited by charge transfer

Characteristics of ovulation method acceptors: a cross-cultural assessment.

PubMed

Klaus, H; Labbok, M; Barker, D

1988-01-01

Five programs of instruction in the ovulation method (OM) in diverse geographic and cultural settings are described, and characteristics of approximately 200 consecutive OM acceptors in each program are examined. Major findings include: the religious background and family size of acceptors are variable, as is the level of previous contraceptive use. Acceptors are drawn from a wide range of socioeconomic and religious backgrounds; however, family planning intention was similarly distributed in all five countries. In sum, the ovulation method is accepted by persons from a variety of backgrounds within and between cultural setting.

Nonesterified fatty acid accumulation and release during heart muscle-cell (myocyte) injury: modulation by extracellular "acceptor".

PubMed

Janero, D R; Burghardt, C

1989-07-01

Long-chain nonesterified fatty acid (NEFA) accumulation in the heart muscle cell (myocyte) and NEFA release to the extracellular milieu are considered contributors to the pathogenesis of myocardial injury in a number of cardiovascular disease states. Reported here is a study of the factors which influence and control the interactions among NEFA formation, intracellular NEFA accumulation, and NEFA release to the extracellular compartment by the irreversibly injured myocyte. Under conditions of metabolic inhibition, neonatal rat myocytes in primary monolayer culture became virtually depleted of ATP within 8 h. The metabolically inhibited myocytes evidenced membrane phospholipid degradation and a resultant net accumulation of NEFA produced thereby in the extracellular medium. However, under conditions of nutrient deprivation, the injured myocytes retained the NEFA produced from phospholipid catabolism intracellularly and did not release it to the culture medium, although the extent of myocyte ATP depletion was the same as it had been from metabolic inhibition. Serum could elicit, in a concentration-dependent fashion, the quantitative release of NEFA from metabolically inhibited myocytes to the culture medium but did not influence the net production of NEFA by the injured cells. Similarly, NEFA release from nutrient-deprived myocytes incubated in serum-free, substrate-free medium or in physiological buffer could be induced by supplementing the medium or buffer with bovine serum albumin (BSA), and the extent of NEFA release, but not NEFA formation, was dependent upon the extracellular BSA concentration. No manipulations to media other than changing their serum content or supplementing them with BSA were found to influence the disposition of NEFA produced during phospholipid catabolism in the irreversibly injured, ATP-depleted myocyte. Therefore, although progressive metabolic compromise in the myocyte was correlated with increasing, net NEFA formation, the distribution

Recovery of fission product palladium from acidic high level waste solutions

DOE Office of Scientific and Technical Information (OSTI.GOV)

Rizvi, G.H.; Mathur, J.N.; Murali, M.S.

1996-07-01

The recovery of palladium from a synthetic pressurized heavy water reactor high level waste (PHWR-HLW) solution has been carried out, and the best reagents to use for the actual HLW solutions are discussed. The extraction of palladium from nitric acid solutions has been carried out using Cyanex-471X (triisobutylphosphine sulfide, TIPS) as the extractant. The metal ion could be quantitatively extracted from solutions with nitric acid concentrations between 2.0 and 6.0 M. The species extracted into the organic phase was found to be Pd(NO{sub 3}){sub 2}{center_dot}TIPS. Nitric acid in the range of 2.0 to 5.0 M had no effect on TIPSmore » for at least 71 hours. A systematic study of gamma irradiation on loading and stripping of palladium from loaded organic phases using several potential extractants, TIPS, alpha benzoin oxime, dioctylsulfide, and dioctylsulfoxide has been made. A flow sheet for the recovery of palladium from actual HLW solutions using TIPS is proposed.« less

The ototoxic effect of boric acid solutions applied into the middle ear of guinea pigs.

PubMed

Oztürkcan, Sedat; Dündar, Riza; Katilmis, Hüseyin; Ilknur, Ali Ekber; Aktaş, Sinem; Haciömeroğlu, Senem

2009-05-01

This study analyzed the ototoxic effects of boric acid solutions. Boric acid solutions have been used as otologic preparations for many years. Boric acid is commonly found in solutions prepared with alcohol or distilled water but can also be found in a powder form. These preparations are used for both their antiseptic and acidic qualities in external and middle ear infections. We investigated the ototoxic effect of boric acid solutions on guinea pigs. We are unaware of any similar, previously published study of this subject in English. The study was conducted on 28 young albino guinea pigs. Prior to application of the boric acid solution under general anesthesia, an Auditory Brainstem Response (ABRs) test was applied to the right ear of the guinea pigs. Following the test, a perforation was created on the tympanic membrane of the right ear of each guinea pig and small gelfoam pieces were inserted into the perforated area. Test solutions were administered to the middle ear for 10 days by means of a transcanal route. Fifteen days after inserting the gelfoams in all of the guinea pigs, we anasthesized the guinea pigs and removed the gelfoams from the perforated region of the ear and then performed an ABRs on each guinea pig. The ABRs were within the normal range before the applications. After the application, no significant changes were detected in the ABRs thresholds in neither the saline group nor the group administered boric acid and distilled water solution; however, significant changes were detected in the ABRs thresholds of the Gentamicine and boric acid and alcohol solution groups. We believe that a 4% boric acid solution prepared with distilled water can be a more reliable preparation than a 4% boric acid solution prepared with alcohol.

Acceptor Specificity of the Pasteurella Hyaluronan and Chondroitin Synthases and Production of Chimeric Glycosaminoglycans*†

PubMed Central

Tracy, Breca S.; Avci, Fikri Y.; Linhardt, Robert J.; DeAngelis, Paul L.

2014-01-01

The hyaluronan (HA) synthase, PmHAS, and the chondroitin synthase, PmCS, from the Gram-negative bacterium Pasteurella multocida polymerize the glycosaminoglycan (GAG) sugar chains HA or chondroitin, respectively. The recombinant Escherichia coli-derived enzymes were shown previously to elongate exogenously supplied oligosaccharides of their cognate GAG (e.g. HA elongated by PmHAS). Here we show that oligosaccharides and polysaccharides of certain noncognate GAGs (including sulfated and iduronic acid-containing forms) are elongated by PmHAS (e.g. chondroitin elongated by PmHAS) or PmCS. Various acceptors were tested in assays where the synthase extended the molecule with either a single monosaccharide or a long chain (~102–4 sugars). Certain GAGs were very poor acceptors in comparison to the cognate molecules, but elongated products were detected nonetheless. Overall, these findings suggest that for the interaction between the acceptor and the enzyme (a) the orientation of the hydroxyl at the C-4 position of the hexosamine is not critical, (b) the conformation of C-5 of the hexuronic acid (glucuronic versus iduronic) is not crucial, and (c) additional negative sulfate groups are well tolerated in certain cases, such as on C-6 of the hexosamine, but others, including C-4 sulfates, were not or were poorly tolerated. In vivo, the bacterial enzymes only process unsulfated polymers; thus it is not expected that the PmCS and PmHAS catalysts would exhibit such relative relaxed sugar specificity by acting on a variety of animal-derived sulfated or epimerized GAGs. However, this feature allows the chemoenzymatic synthesis of a variety of chimeric GAG polymers, including mimics of proteoglycan complexes. PMID:17099217

Part I. Synthesis and characterization of donor-pi-acceptor compounds with pentadienyl-bridged indoline and tetrahydroquinoline donors and aldehyde and thiobarbituric acid acceptors Part II. Longitudinal study comparing online versus face-to-face course delivery in introductory chemistry

NASA Astrophysics Data System (ADS)

Greco, Patrick F.

Part I. The design and development of organic second-order nonlinear optical (NLO) materials have attracted much interest due to their applications in optoelectronic devices and modern communications technology. Donor-pi-acceptor compounds, D-(CH=CH)n-A, often exhibit hyperpolarizability that results in laser frequency doubling (second harmonic generation) and spectroscopic solvatochromism. To study the effect of donor amine geometry upon properties associated with second-order NLO behavior in simple donor-pi-acceptor compounds, equilibrium geometries and hyperpolarizabilities (beta) for donor-acceptor polyenes with amine donors were calculated at several levels of computational theory. Two new molecules with donors that only differ by one methylene group were chosen for comparison. Thus, 5-(N-methylindolin-5-yl)-2, 4-pentadienal (1a) and 5-(N-methyl-2, 3, 4-trihydroquinolin-6-yl)-2, 4-pentadienal (2a) were synthesized in two steps from starting materials described in the literature. These aldehydes were converted into stronger acceptors in one step to give diethylthiobarbituric acid derivatives 1c and 2c, as well as tricyanofuran derivatives 1d and 2d. Positive UV solvatochromism was observed in all three derivatives. NMR solvatochromism was most pronounced in 1c, and 2c vs. 1a and 2a as measured by changes in chemical shifts. Additionally, coupling constants showed more conjugation in 1c and 2c, where 1a and 2a showed less conjugation. Finally, differential scanning calorimetry and thermal gravimetric analysis were used to compare decomposition and melting temperatures of these compounds to determine their stability. Aldehydes, 1a and 2a had distinct melting points, while the 1c, 2c, 1d, and 2d derivatives decomposed at temperatures above 150 °C. Part II. This longitudinal study focused on an introductory chemistry course taught using two different modes of delivery: online and face-to-face (FtF). The sections of the course using the different delivery modes

A Coupling of Benzamides and Donor/Acceptor Diazo–Compounds to form γ-Lactams via Rh(III)–Catalyzed C–H Activation

PubMed Central

Hyster, Todd K.; Ruhl, Kyle E.; Rovis, Tomislav

2013-01-01

The coupling of O-pivaloyl benzhydroxamic acids with donor/acceptor diazo compounds provides iso-indolones in high yield. The reaction tolerates a broad range of benzhydroxamic acids and diazo compounds including substituted 2,2,2-trifluorodiazo ethanes. Mechanistic experiments suggest that C–H activation is turnover limiting and irreversible, while insertion of the diazo compound favors electron deficient substrates. PMID:23548055

Removal of radium from acidic solutions containing same by adsorption on coal fly ash

DOEpatents

Scheitlin, Frank M.

1984-01-01

The invention is a process for the removal of radium from acidic aqueous solutions. In one aspect, the invention is a process for removing radium from an inorganic-acid solution. The process comprises contacting the solution with coal fly ash to effect adsorption of the radium on the ash. The radium-containing ash then is separated from the solution. The process is simple, comparatively inexpensive, and efficient. High radium-distribution coefficients are obtained even at room temperature. Coal fly ash is an inexpensive, acid-resistant, high-surface-area material which is available in large quantities throughout the United States. The invention is applicable, for example, to the recovery of .sup.226 Ra from nitric acid solutions which have been used to leach radium from uranium-mill tailings.

Solution Preserves Nucleic Acids in Body-Fluid Specimens

NASA Technical Reports Server (NTRS)

Pierson, Duane L.; Stowe, Raymond P.

2004-01-01

A solution has been formulated to preserve deoxyribonucleic acid (DNA) and ribonucleic acid (RNA) in specimens of blood, saliva, and other bodily fluids. Specimens of this type are collected for diagnostic molecular pathology, which is becoming the method of choice for diagnosis of many diseases. The solution makes it possible to store such specimens at room temperature, without risk of decomposition, for subsequent analysis in a laboratory that could be remote from the sampling location. Thus, the solution could be a means to bring the benefits of diagnostic molecular pathology to geographic regions where refrigeration equipment and diagnostic laboratories are not available. The table lists the ingredients of the solution. The functions of the ingredients are the following: EDTA chelates divalent cations that are necessary cofactors for nuclease activity. In so doing, it functionally removes these cations and thereby retards the action of nucleases. EDTA also stabilizes the DNA helix. Tris serves as a buffering agent, which is needed because minor contaminants in an unbuffered solution can exert pronounced effects on pH and thereby cause spontaneous degradation of DNA. SDS is an ionic detergent that inhibits ribonuclease activity. SDS has been used in some lysis buffers and as a storage buffer for RNA after purification. The use of the solution is straightforward. For example, a sample of saliva is collected by placing a cotton roll around in the subject's mouth until it becomes saturated, then the cotton is placed in a collection tube. Next, 1.5 mL of the solution are injected directly into the cotton and the tube is capped for storage at room temperature. The effectiveness of the solution has been demonstrated in tests on specimens of saliva containing herpes simplex virus. In the tests, the viral DNA, as amplified by polymerase chain reaction, was detected even after storage for 120 days.

Hydrophobic interactions between polymethacrylic acid and sodium laureth sulfate in aqueous solutions

NASA Astrophysics Data System (ADS)

Yaremko, Z. M.; Fedushinskaya, L. B.; Burka, O. A.; Soltys, M. N.

2014-09-01

The role of hydrophobic interaction in the development of associative processes is demonstrated, based on the concentration dependences of the viscosity and pH of binary solutions of polymethacrylic acid as an anionic polyelectrolyte and sodium laureth sulfate as an anionic surfactant. It is found that the inflection point on the dependence of the difference between the pH values of binary solutions of polymethacrylic acid and sodium laureth sulfate on the polyelectrolyte concentration is a criterion for determining the predominant contribution from hydrophobic interaction, as is the inflection point on the dependence of pH of individual solutions of polymethacrylic acid on the polyelectrolyte concentration.

Impact of fluorescent lighting on the browning potential of model wine solutions containing organic acids and iron.

PubMed

Grant-Preece, Paris; Barril, Celia; Schmidtke, Leigh M; Clark, Andrew C

2018-03-15

Model wine solutions containing organic acids, individually or combined, and iron(III), were exposed to light from fluorescent lamps or stored in darkness for four hours. (-)-Epicatechin was then added, and the solutions incubated in darkness for 10days. Browning was monitored by UV-visible absorption spectrophotometry and UHPLC-DAD. The pre-irradiated solutions containing tartaric acid exhibited increased yellow/brown coloration compared to the dark controls mainly due to reaction of the tartaric acid photodegradation product glyoxylic acid with (-)-epicatechin to form xanthylium cation pigments. In these solutions, browning decreased as the concentrations of organic acids other than tartaric acid increased. Xanthylium cations were also detected in the pre-irradiated malic acid solution. However, in the malic acid, succinic acid, citric acid and lactic acid solutions, any coloration was mainly due to the production of dehydrodiepicatechin A, which was largely independent of prior light exposure, but strongly affected by the organic acid present. Copyright © 2017 Elsevier Ltd. All rights reserved.

Micro-organization of humic acids in aqueous solutions

NASA Astrophysics Data System (ADS)

Klučáková, Martina; Věžníková, Kateřina

2017-09-01

The methods of dynamic light scattering and micro-rheology were used to investigate the molecular organization of humic acids in solutions. The obtained results were supplemented by ultraviolet/visible spectrometry and measurement of the zeta potential. Particle tracking micro-rheology was used for the first time as a novel method in humic research. Solutions of humic acids were prepared in three different mediums: NaOH, NaCl, and NaOH neutralized by HCl after dissolution of the humic sample. The molecular organization of humic acids was studied over a wide concentration range (0.01-10 g dm-3). Two breaks were detected in the obtained concentration dependencies. The rearrangements were observed at concentrations around 0.02 g dm-3 and 1 g dm-3. Changes in the measured values observed at around 0.02 g dm-3 were less noticeable and were related to the formation of particles between 100 and 1000 nm in size and the strong bimodal character of humic systems diluted by NaCl. The ;switch-over point; at around 1 g dm-3 indicated changes in the secondary structure of humic acids connected with the increase in colloidal stability (decrease of zeta potential), the decrease in polydispersity, and minimal values of viscosity.

Impact on electronic structure of donor/acceptor blend in organic photovoltaics by decontamination of molybdenum-oxide surface

NASA Astrophysics Data System (ADS)

Ito, Yuta; Akaike, Kouki; Fukuda, Takeshi; Sato, Daisuke; Fuse, Takuya; Iwahashi, Takashi; Ouchi, Yukio; Kanai, Kaname

2018-05-01

Molybdenum oxide (MoOx) is widely used as the hole-transport layer in bulk-heterojunction organic photovoltaics (BHJ-OPVs). During the fabrication of solution-processed BHJ-OPVs on vacuum-deposited MoOx film, the film must be exposed to N2 atmosphere in a glove box, where the donor/acceptor blends are spin-coated from a mixed solution. Employing photoelectron spectroscopy, we reveal that the exposure of the MoOx film to such atmosphere contaminates the MoOx surface. Annealing the contaminated MoOx film at 160 °C for 5 min, prior to spin-coating the blend film, can partially remove the carbon and oxygen adsorbed on the MoOx surface during the exposure of MoOx. However, the contamination layer on the MoOx surface does not affect the energy-level alignment at the interface between MoOx and the donor/acceptor blend. Hence, significant improvement in the performance of BHJ-OPVs by mildly annealing the MoOx layer, which was previously reported, can be explained by the reduction of undesired contamination.

Characteristics of contraceptive acceptors in an urban Nigerian setting.

PubMed

Ayangade, O

1984-02-01

Intensive efforts in promoting family planning concepts and contraceptive delivery in the Third World over the past two- and one-half decades have yielded only token dividends . This has occurred in Nigeria, despite the favorable government attitude. A study of the characteristics of current contraceptive acceptors showed an overwhelming percentage of acceptors are uneducated , married and from the lower socioeconomic class, a striking departure from usual expectations. Most acceptors prefer oral contraceptives. The status of acceptance of modern contraception by the educated population is still undetermined. Contraceptives appeared to be used primarily by women aged 30 and older in our population.

Organic electronic devices with multiple solution-processed layers

DOEpatents

Forrest, Stephen R.; Lassiter, Brian E.; Zimmerman, Jeramy D.

2015-08-04

A method of fabricating a tandem organic photosensitive device involves depositing a first layer of an organic electron donor type material film by solution-processing of the organic electron donor type material dissolved in a first solvent; depositing a first layer of an organic electron acceptor type material over the first layer of the organic electron donor type material film by a dry deposition process; depositing a conductive layer over the interim stack by a dry deposition process; depositing a second layer of the organic electron donor type material over the conductive layer by solution-processing of the organic electron donor type material dissolved in a second solvent, wherein the organic electron acceptor type material and the conductive layer are insoluble in the second solvent; depositing a second layer of an organic electron acceptor type material over the second layer of the organic electron donor type material film by a dry deposition process, resulting in a stack.

Method for liquid chromatographic extraction of strontium from acid solutions

DOEpatents

Horwitz, E. Philip; Dietz, Mark L.

1992-01-01

A method and apparatus for extracting strontium and technetium values from biological, industrial and environmental sample solutions using a chromatographic column is described. An extractant medium for the column is prepared by generating a solution of a diluent containing a Crown ether and dispersing the solution on a resin substrate material. The sample solution is highly acidic and is introduced directed to the chromatographic column and strontium or technetium is eluted using deionized water.

49 CFR 173.229 - Chloric acid solution or chlorine dioxide hydrate, frozen.

Code of Federal Regulations, 2012 CFR

2012-10-01

... 49 Transportation 2 2012-10-01 2012-10-01 false Chloric acid solution or chlorine dioxide hydrate... Than Class 1 and Class 7 § 173.229 Chloric acid solution or chlorine dioxide hydrate, frozen. When the.... Fiberboard boxes must be reinforced and insulated and sufficient dry ice must be used to maintain the hydrate...

49 CFR 173.229 - Chloric acid solution or chlorine dioxide hydrate, frozen.

Code of Federal Regulations, 2013 CFR

2013-10-01

... 49 Transportation 2 2013-10-01 2013-10-01 false Chloric acid solution or chlorine dioxide hydrate... Than Class 1 and Class 7 § 173.229 Chloric acid solution or chlorine dioxide hydrate, frozen. When the.... Fiberboard boxes must be reinforced and insulated and sufficient dry ice must be used to maintain the hydrate...

49 CFR 173.229 - Chloric acid solution or chlorine dioxide hydrate, frozen.

Code of Federal Regulations, 2010 CFR

2010-10-01

... 49 Transportation 2 2010-10-01 2010-10-01 false Chloric acid solution or chlorine dioxide hydrate... Than Class 1 and Class 7 § 173.229 Chloric acid solution or chlorine dioxide hydrate, frozen. When the.... Fiberboard boxes must be reinforced and insulated and sufficient dry ice must be used to maintain the hydrate...

49 CFR 173.229 - Chloric acid solution or chlorine dioxide hydrate, frozen.

Code of Federal Regulations, 2011 CFR

2011-10-01

... 49 Transportation 2 2011-10-01 2011-10-01 false Chloric acid solution or chlorine dioxide hydrate... Than Class 1 and Class 7 § 173.229 Chloric acid solution or chlorine dioxide hydrate, frozen. When the.... Fiberboard boxes must be reinforced and insulated and sufficient dry ice must be used to maintain the hydrate...

49 CFR 173.229 - Chloric acid solution or chlorine dioxide hydrate, frozen.

Code of Federal Regulations, 2014 CFR

2014-10-01

... 49 Transportation 2 2014-10-01 2014-10-01 false Chloric acid solution or chlorine dioxide hydrate... Than Class 1 and Class 7 § 173.229 Chloric acid solution or chlorine dioxide hydrate, frozen. When the.... Fiberboard boxes must be reinforced and insulated and sufficient dry ice must be used to maintain the hydrate...

The Impact of Acceptor-Acceptor Homocoupling on the Optoelectronic Properties and Photovoltaic Performance of PDTSQxff Low Bandgap Polymers.

PubMed

Pirotte, Geert; Kesters, Jurgen; Cardeynaels, Tom; Verstappen, Pieter; D'Haen, Jan; Lutsen, Laurence; Champagne, Benoît; Vanderzande, Dirk; Maes, Wouter

2018-04-22

Push-pull-type conjugated polymers applied in organic electronics do not always contain a perfect alternation of donor and acceptor building blocks. Misscouplings can occur, which have a noticeable effect on the device performance. In this work, the influence of homocoupling on the optoelectronic properties and photovoltaic performance of PDTSQx ff polymers is investigated, with a specific focus on the quinoxaline acceptor moieties. A homocoupled biquinoxaline segment is intentionally inserted in specific ratios during the polymerization. These homocoupled units cause a gradually blue-shifted absorption, while the highest occupied molecular orbital energy levels decrease only significantly upon the presence of 75-100% of homocouplings. Density functional theory calculations show that the homocoupled acceptor unit generates a twist in the polymer backbone, which leads to a decreased conjugation length and a reduced aggregation tendency. The virtually defect-free PDTSQx ff affords a solar cell efficiency of 5.4%, which only decreases substantially upon incorporating a homocoupling degree over 50%. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Spatial structure of single and interacting Mn acceptors in GaAs

NASA Astrophysics Data System (ADS)

Koenraad, Paul

2005-03-01

Ferromagnetic semiconductors such as Ga1-xMnxAs are receiving a lot of attention at the moment because of their application in spintronic devices. However, despite intense study of deep acceptors in III-V semiconductors such as MnGa, little information has been obtained on their electronic properties at the atomic scale. Yet the spatial shape of the Mn acceptor state will influence the hole-mediated Mn-Mn coupling and thus all of the magnetic properties of ferromagnetic semiconductors such as Ga1-xMnxAs. This study presents an experimental and theoretical description of the spatial symmetry of the Mn acceptor wave-function in GaAs. We present measurements of the spatial mapping of the anisotropic wavefunction of a hole localized at a Mn acceptor. To achieve this, we have used the STM tip not only to image the Mn acceptor but also to manipulate its charge state A^0/A^- at room temperature. Within an envelope function effective mass model (EFM) the anisotropy in the acceptor wave-function can be traced to the influence of the cubic symmetry of the GaAs crystal which selects specific d-states that mix into the ground state due to the spin-orbit interaction in the valence band. Comparison with calculations based on a tight-binding model (TBM) for the Mn acceptor structure supports this conclusion. Using the same experimental and theoretical approach we furthermore explored the interaction between Mn acceptors directly by analyzing close Mn-Mn pairs, which were separated by less than 2 nm. We will discuss some implications of these results for Mn delta-doped layers grown on differently oriented growth surfaces.

Next-generation organic photovoltaics based on non-fullerene acceptors

NASA Astrophysics Data System (ADS)

Cheng, Pei; Li, Gang; Zhan, Xiaowei; Yang, Yang

2018-03-01

Over the past three years, a particularly exciting and active area of research within the field of organic photovoltaics has been the use of non-fullerene acceptors (NFAs). Compared with fullerene acceptors, NFAs possess significant advantages including tunability of bandgaps, energy levels, planarity and crystallinity. To date, NFA solar cells have not only achieved impressive power conversion efficiencies of 13-14%, but have also shown excellent stability compared with traditional fullerene acceptor solar cells. This Review highlights recent progress on single-junction and tandem NFA solar cells and research directions to achieve even higher efficiencies of 15-20% using NFA-based organic photovoltaics are also proposed.

High speed nucleic acid sequencing

DOEpatents

Korlach, Jonas [Ithaca, NY; Webb, Watt W [Ithaca, NY; Levene, Michael [Ithaca, NY; Turner, Stephen [Ithaca, NY; Craighead, Harold G [Ithaca, NY; Foquet, Mathieu [Ithaca, NY

2011-05-17

The present invention is directed to a method of sequencing a target nucleic acid molecule having a plurality of bases. In its principle, the temporal order of base additions during the polymerization reaction is measured on a molecule of nucleic acid. Each type of labeled nucleotide comprises an acceptor fluorophore attached to a phosphate portion of the nucleotide such that the fluorophore is removed upon incorporation into a growing strand. Fluorescent signal is emitted via fluorescent resonance energy transfer between the donor fluorophore and the acceptor fluorophore as each nucleotide is incorporated into the growing strand. The sequence is deduced by identifying which base is being incorporated into the growing strand.

Efficient Incorporation of Mg in Solution Grown GaN Crystals

NASA Astrophysics Data System (ADS)

Freitas, Jaime A., Jr.; Feigelson, Boris N.; Anderson, Travis J.

2013-11-01

Detailed spectrometry and optical spectroscopy studies carried out on GaN crystals grown in solution detect and identify Mg as the dominant shallow acceptor. Selective etching of crystals with higher Mg levels than that of the donor concentration background indicates that Mg acceptors incorporate preferentially in the N-polar face. Electrical transport measurements verified an efficient incorporation and activation of the Mg acceptors. These results suggest that this growth method has the potential to produce p-type doped epitaxial layers or p-type substrates characterized by high hole concentration and low defect density.

Molecular helices as electron acceptors in high-performance bulk heterojunction solar cells

DOE PAGES

Yu M. Zhong; Nam, Chang -Yong; Trinh, M. Tuan; ...

2015-09-18

Despite numerous organic semiconducting materials synthesized for organic photovoltaics in the past decade, fullerenes are widely used as electron acceptors in highly efficient bulk-heterojunction solar cells. None of the non-fullerene bulk heterojunction solar cells have achieved efficiencies as high as fullerene-based solar cells. Design principles for fullerene-free acceptors remain unclear in the field. Here we report examples of helical molecular semiconductors as electron acceptors that are on par with fullerene derivatives in efficient solar cells. We achieved an 8.3% power conversion efficiency in a solar cell, which is a record high for non-fullerene bulk heterojunctions. Femtosecond transient absorption spectroscopy revealedmore » both electron and hole transfer processes at the donor–acceptor interfaces. Atomic force microscopy reveals a mesh-like network of acceptors with pores that are tens of nanometres in diameter for efficient exciton separation and charge transport. As a result, this study describes a new motif for designing highly efficient acceptors for organic solar cells.« less

Molecular helices as electron acceptors in high-performance bulk heterojunction solar cells.

PubMed

Zhong, Yu; Trinh, M Tuan; Chen, Rongsheng; Purdum, Geoffrey E; Khlyabich, Petr P; Sezen, Melda; Oh, Seokjoon; Zhu, Haiming; Fowler, Brandon; Zhang, Boyuan; Wang, Wei; Nam, Chang-Yong; Sfeir, Matthew Y; Black, Charles T; Steigerwald, Michael L; Loo, Yueh-Lin; Ng, Fay; Zhu, X-Y; Nuckolls, Colin

2015-09-18

Despite numerous organic semiconducting materials synthesized for organic photovoltaics in the past decade, fullerenes are widely used as electron acceptors in highly efficient bulk-heterojunction solar cells. None of the non-fullerene bulk heterojunction solar cells have achieved efficiencies as high as fullerene-based solar cells. Design principles for fullerene-free acceptors remain unclear in the field. Here we report examples of helical molecular semiconductors as electron acceptors that are on par with fullerene derivatives in efficient solar cells. We achieved an 8.3% power conversion efficiency in a solar cell, which is a record high for non-fullerene bulk heterojunctions. Femtosecond transient absorption spectroscopy revealed both electron and hole transfer processes at the donor-acceptor interfaces. Atomic force microscopy reveals a mesh-like network of acceptors with pores that are tens of nanometres in diameter for efficient exciton separation and charge transport. This study describes a new motif for designing highly efficient acceptors for organic solar cells.

Effect of citric acid on the acidification of artificial pepsin solution for metacercariae isolation from fish.

PubMed

Kim, Min-Ki; Pyo, Kyoung-Ho; Hwang, Young-Sang; Chun, Hyang Sook; Park, Ki Hwan; Ko, Seong-Hee; Chai, Jong-Yil; Shin, Eun-Hee

2013-11-15

Artificial digestive solution based on pepsin is essential for collecting metacercariae from fish. To promote the enzymatic reactivity of pepsin, the pH of the solution has to be adjusted to pH 1.0-2.0. Hydrochloride (HCl) is usually used for this purpose, but the use of HCl raises safety concerns. The aim of this work was to address the usefulness of citric acid as an alternative for HCl for the acidification of pepsin solution, and to examine its potential to damage metacercariae during in vitro digestion as compared with HCl. Changes in pH after adding 1-9% of citric acid (m/v) to pepsin solution were compared to a 1% HCl (v/v) addition. Digestion of fish muscle was evaluated by measuring released protein concentrations by spectrophotometry. In addition, survival rates of metacercariae in pepsin solution were determined at different citric acid concentrations and were compared that of with 1% HCl. The present study shows that addition of citric acid reduced the pH of pepsin solutions to the required level. Addition of more than 5% of citric acid resulted in the effective digestion of fish muscle over 3h in vitro, and 5% citric acid was less lethal to metacercariae than 1% HCl in pepsin solution. Pepsin solution containing 5% citric acid had digestive capacity superior to pepsin solution containing 1% HCl after 3h incubation with released protein concentrations of 12.0 ng/ml for 5% citric acid and 9.6 ng/ml for 1% HCl. Accordingly, the present study suggests that the addition of 5% citric acid to pepsin solution is a good alternative to 1% HCl in infection studies because citric acid is a stable at room temperature and has a good safety profile. In addition, we suggest that the use of citric acid enables the preparation of commercial digestive solutions for the detection of microorganisms in fish and other vertebrate muscle tissue. Copyright © 2013 The Authors. Published by Elsevier B.V. All rights reserved.

Investigating charge generation in polymer:non-fullerene acceptor bulk heterojunction films

DOE PAGES

Stoltzfus, Dani M.; Larson, Bryon W.; Zarrabi, Nasim; ...

2018-01-31

Non-fullerene acceptors are now capable of being used in high efficiency bulk heterojunction (BHJ) donor-acceptor organic solar cells. Acceptors comprising single or multiple linked chromophores have been used. We have developed a new non-fullerene molecular acceptor as well as two non-polymeric macromolecular materials that contain four equivalents of a similar chromophore, but can adopt different spatial arrangements of the chromophores. We compare the effect of having single and multiple chromophores within a macromolecule on the charge generation processes in P3HT:non-fullerene acceptor BHJ films using Transient Absorption Spectroscopy (TAS) and Time Resolved Microwave Conductivity (TRMC) measurements. It was found from themore » TAS measurements that at low weight percent (5 wt%) the single chromophore formed more polarons than the acceptors in which chromophores were linked, due to it having a more even distribution within the film. At higher concentrations (50 wt%) the trend was reversed due to the single chromophore forming crystalline domains, which reduced the interface area with the P3HT donor. The TRMC measurements showed that more mobile carriers were formed in the macromolecular acceptors when used at low concentrations in the blend and, independent of concentration, mobile carriers had a longer lifetime when compared to films containing the molecular material, which we ascribe to the charges being able to sample more than one chromophore and thus reduce recombination events.« less

PROCESS OF SECURING PLUTONIUM IN NITRIC ACID SOLUTIONS IN ITS TRIVALENT OXIDATION STATE

DOEpatents

Thomas, J.R.

1958-08-26

>Various processes for the recovery of plutonium require that the plutonium be obtalned and maintained in the reduced or trivalent state in solution. Ferrous ions are commonly used as the reducing agent for this purpose, but it is difficult to maintain the plutonium in a reduced state in nitric acid solutions due to the oxidizing effects of the acid. It has been found that the addition of a stabilizing or holding reductant to such solution prevents reoxidation of the plutonium. Sulfamate ions have been found to be ideally suitable as such a stabilizer even in the presence of nitric acid.

Three holes bound to a double acceptor - Be(+) in germanium

NASA Technical Reports Server (NTRS)

Haller, E. E.; Mcmurray, R. E., Jr.; Falicov, L. M.; Haegel, N. M.; Hansen, W. L.

1983-01-01

A double acceptor binding three holes has been observed for the first time with photoconductive far-infrared spectroscopy in beryllium-doped germanium single crystals. This new center, Be(+), has a hole binding energy of about 5 meV and is only present when free holes are generated by ionization of either neutral shallow acceptors or neutral Be double acceptors. The Be(+) center thermally ionizes above 4 K. It disappears at a uniaxial stress higher than about a billion dyn/sq cm parallel to (111) as a result of the lifting of the valence-band degeneracy.

Improving Photoconductance of Fluorinated Donors with Fluorinated Acceptors

DOE Office of Scientific and Technical Information (OSTI.GOV)

Garner, Logan E.; Larson, Bryon; Oosterhout, Stefan

2016-11-21

This work investigates the influence of fluorination of both donor and acceptor materials on the generation of free charge carriers in small molecule donor/fullerene acceptor BHJ OPV active layers. A fluorinated and non-fluorinated small molecule analogue were synthesized and their optoelectronic properties characterized. The intrinsic photoconductance of blends of these small molecule donors was investigated using time-resolved microwave conductivity. Blends of the two donor molecules with a traditional non-fluorinated fullerene (PC70BM) as well as a fluorinated fullerene (C60(CF3)2-1) were investigated using 5% and 50% fullerene loading. We demonstrate for the first time that photoconductance in a 50:50 donor:acceptor BHJ blendmore » using a fluorinated fullerene can actually be improved relative to a traditional non-fluorinated fullerene by fluorinating the donor molecule as well.« less

Structure of polyacrylic acid and polymethacrylic acid solutions : a small angle neutron scattering study

NASA Astrophysics Data System (ADS)

Moussaid, A.; Schosseler, F.; Munch, J. P.; Candau, S. J.

1993-04-01

The intensity scattered from polyacrylic acid and polymethacrylic acid solutions has been measured by small angle neutron scattering experiemnts. The influence of polymer concentration, ionization degree, temperature and salt content has been investigated. Results are in qualitative agreement with a model which predicts the existence of microphases in the unstable region of the phase diagram. Quantitative comparison with the theory is performed by fitting the theoretical structure factor to the experimental data. For a narrow range of ionizaiton degrees nearly quantitative agreement with the theory is found for the polyacrylic acide system.

Regulation of lecithin-cholesterol acyltransferase reaction by acyl acceptors and demonstration of its "idling" reaction.

PubMed

Czarnecka, H; Yokoyama, S

1993-09-15

The mechanism for regulation of cholesterol esterification by lecithin-cholesterol acyltransferase (LCAT) was studied using the highly isolated enzyme from pig plasma. In the reaction with phosphatidylcholine small unilamellar vesicles, cholesterol, water, diacylglycerol, and lysophosphatidylcholine were all potent acceptors of an acyl group cleaved from the sn-2 position of egg phosphatidylcholine, generating cholesteryl ester, free fatty acid, triglyceride, and phosphatidylcholine, respectively. All of these reactions required activation by human apolipoprotein A-I, suggesting that this activation leads to the deacylation of phosphatidylcholine. Those acceptors competed against each other in this vesicle reaction system, and cholesterol was the most potent acyl acceptor. Lysophosphatidylcholine that was endogenously generated by deacylation of phosphatidylcholine in the first step of the LCAT reaction was also a good acyl acceptor, showing that the reaction is always partly "idling." Bovine serum albumin partially inhibited this idling reaction in a concentration-dependent manner up to 80% at 0.60 mM. The above results were essentially reproducible with high density lipoprotein, except that cholesterol is less potent than lysophosphatidylcholine in accepting the acyl group under the condition used. Unlike the apolipoprotein A-I-activated reaction, cholesterol was esterified only slightly by the LCAT reaction on low density lipoprotein and, consequently, did not compete against lysophosphatidylcholine for generation of phosphatidylcholine. Thus, apoB may activate LCAT in a very different manner from apoA-I. The rate of esterification of lysophosphatidylcholine on low density lipoprotein was one-tenth of that on the vesicles and on high density lipoprotein. Thus, LCAT is active on low density lipoprotein but mostly idling as deacylating and reacylating glycerophospholipids.

Acceptor binding energies in GaN and AlN

NASA Astrophysics Data System (ADS)

Mireles, Francisco; Ulloa, Sergio E.

1998-08-01

We employ effective-mass theory for degenerate hole bands to calculate the acceptor binding energies for Be, Mg, Zn, Ca, C, and Si substitutional acceptors in GaN and AlN. The calculations are performed through the 6×6 Rashba-Sheka-Pikus and the Luttinger-Kohn matrix Hamiltonians for wurtzite (WZ) and zinc-blende (ZB) crystal phases, respectively. An analytic representation for the acceptor pseudopotential is used to introduce the specific nature of the impurity atoms. The energy shift due to polaron effects is also considered in this approach. The ionization energy estimates are in very good agreement with those reported experimentally in WZ GaN. The binding energies for ZB GaN acceptors are all predicted to be shallower than the corresponding impurities in the WZ phase. The binding-energy dependence upon the crystal-field splitting in WZ GaN is analyzed. Ionization levels in AlN are found to have similar ``shallow'' values to those in GaN, but with some important differences which depend on the band structure parametrizations, especially the value of the crystal-field splitting used.

Electrochemical and surface analysis of the Fe-Cr-Ru system in non-oxidizing acid solutions

NASA Astrophysics Data System (ADS)

Tjong, S. C.

1990-03-01

The effect of ruthenium addition on the spontaneous passivation behaviour of Fe-40Cr alloy in 0.5M H 2SO 4 and 0.5M HCl acid solutions has been studied. Auger and XPS techniques were also used to investigate the surface chemistries of the spontaneously passivated film. Electrochemical measurements indicate that the Fe-40Cr-0.1Ru and Fe-40Cr-0.2Ru alloys exhibit spontaneous passivation upon exposing them in both hydrochloric and sulphuric acid solutions from 25 to 85 ° C. However, the transition time for spontaneous passivation reduces dramatically with an increase in the ruthenium content and solution temperature. Furthermore, this transition time also decreases for the investigated alloys exposed in a less aggressive sulphuric acid solution. AES results show that ruthenium and chromium are enriched in the spontaneous passive films formed on the Fe-40Cr-0.1Ru alloy in both hydrochloric and sulphuric acid solutions at 25 °C, and also in the spontaneous passive film formed on the Fe-40Cr-0.2Ru alloy in hydrochloric acid solution at 25 ° C. AES does not detect the presence of ruthenium in the spontaneous passive film formed on the Fe-40Cr-0.2Ru alloy in sulphuric acid solution. However, XPS analysis shows that ruthenium and chromium are incorporated into the spontaneous passive films formed on the Fe-40Cr-0.1Ru and Fe-40Cr-0.2Ru alloys in both hydrochloric and sulphuric acid solutions as Ru 4+ and Cr 3+ species.

Effects of the pH and Concentration on the Stability of Standard Solutions of Proteinogenic Amino Acid Mixtures.

PubMed

Kato, Megumi; Yamazaki, Taichi; Kato, Hisashi; Yamanaka, Noriko; Takatsu, Akiko; Ihara, Toshihide

2017-01-01

To prepare metrologically traceable amino acid mixed standard solutions, it is necessary to determine the stability of each amino acid present in the mixed solutions. In the present study, we prepared amino acid mixed solutions using certified reference standards of 17 proteinogenic amino acids, and examined the stability of each of these amino acids in 0.1 N HCl. We found that the concentration of glutamic acid decreased significantly during storage. LC/MS analysis indicated that the instability of glutamic acid was due to the partial degradation of glutamic acid to pyroglutamic acid in 0.1 N HCl. Using accelerated degradation tests, we investigated several solvent compositions to improve the stability of glutamic acid in amino acid mixed solution, and determined that the change of the pH by diluting the mixed solution improved the stability of glutamic acid.

INTERACTION OF AQUEOUS SOLUTIONS OF CHLORINE WITH MALIC ACID, TARTARIC ACID, AND VARIOUS FRUIT JUICES, A SOURCE OF MUTAGENS

EPA Science Inventory

The interactions of aqueous solutions of chlorine with some fruit acids (citric acid, DL-malic acid, and L-tartaric acid) at different pH values were studied. iethyl ether extraction followed by GC/MS analysis indicated that a number of mutagens (certain chlorinated propanones an...

Synthesis, spectral and thermal studies of the newly hydrogen bonded charge transfer complex of o-phenylenediamine with π acceptor picric acid

NASA Astrophysics Data System (ADS)

Khan, Ishaat M.; Ahmad, Afaq

2010-10-01

Newly proton or charge transfer complex [(OPDH) +(PA) -] was synthesized by the reaction of the donor, o-phenylenediamine (OPD) with acceptor, 2,4,6-trinitrophenol (PAH). The chemical reaction has occurred via strong hydrogen bonding followed by migration of proton from acceptor to donor. UV-vis, 1H NMR and FTIR spectra, in addition to the thermal and elemental analysis were used to confirm the proposed occurrence of the chemical reaction and to investigate the newly synthesized solid CT complex. The stoichiometry of the CT complex was found to be 1:1. The formation constant and molar extinction coefficient of the CT complex were evaluated by the Benesi-Hildebrand equation.

2012 Gordon Research Conference, Electron donor-acceptor interactions, August 5-10 2012

DOE Office of Scientific and Technical Information (OSTI.GOV)

McCusker, James

The upcoming incarnation of the Gordon Research Conference on Electron Donor Acceptor Interactions will feature sessions on classic topics including proton-coupled electron transfer, dye-sensitized solar cells, and biological electron transfer, as well as emerging areas such as quantum coherence effects in donor-acceptor interactions, spintronics, and the application of donor-acceptor interactions in chemical synthesis.

Biocompatibility of a bicarbonate-buffered amino-acid-based solution for peritoneal dialysis.

PubMed

Bender, Thorsten O; Witowski, Janusz; Aufricht, Christoph; Endemann, Michaela; Frei, Ulrich; Passlick-Deetjen, Jutta; Jörres, Achim

2008-09-01

Amino-acid-based peritoneal dialysis (PD) fluids have been developed to improve the nutritional status of PD patients. As they may potentially exacerbate acidosis, an amino-acid-containing solution buffered with bicarbonate (Aminobic) has been proposed to effectively maintain acid-base balance. The aim of this study was to evaluate the mesothelial biocompatibility profile of this solution in comparison with a conventional low-glucose-based fluid. Omentum-derived human peritoneal mesothelial cells (HPMC) were preexposed to test PD solutions for up to 120 min, then allowed to recover in control medium for 24 h, and assessed for heat-shock response, viability, and basal and stimulated cytokine [interleukin (IL)-6] and prostaglandin (PGE(2)) release. Acute exposure of HPMC to conventional low-glucose-based PD solution resulted in a time-dependent increase in heat-shock protein (HSP-72) expression, impaired viability, and reduced ability to release IL-6 in response to stimulation. In contrast, in cells treated with Aminobic, the expression of HSP-72 was significantly lower, and viability and cytokine-producing capacity were preserved and did not differ from those seen in control cells. In addition, exposure to Aminobic increased basal release of IL-6 and PGE(2). These data point to a favorable biocompatibility profile of the amino-acid-based bicarbonate-buffered PD solution toward HPMC.

Acidic and basic solutions dissolve protein plugs made of lithostathine complicating choledochal cyst/pancreaticobiliary maljunction.

PubMed

Kaneko, Kenitiro; Ono, Yasuyuki; Tainaka, Takahisa; Sumida, Wataru; Ando, Hisami

2009-07-01

Symptoms of choledochal cysts are caused by protein plugs made of lithostathine, which block the long common channel and increase pancreaticobiliary ductal pressure. Agents that dissolve protein plugs can provide relief from or prevent symptoms. In the present study, drugs reportedly effective for pancreatic and biliary stones were used in dissolution tests. Protein plugs were obtained from choledochal cysts during surgery in two children (5- and 6-year-old girls). Plugs approximately 2 mm in diameter were immersed in citric acid, tartaric acid, dimethadione, bromhexine, dehydrocholic acid, sodium citrate, hydrochloric acid, and sodium hydroxide solutions under observation with a digital microscope. The pH of each solution was measured using a pH meter. Plugs dissolved in citric acid (5.2 mM; pH 2.64), tartaric acid (6.7 mM; pH 2.51), dimethadione (75 mM; pH 3.70), hydrochloric acid (0.5 mM; pH 3.13), and sodium hydroxide (75 mM; pH 12.75) solutions. Plugs did not dissolve in dimethadione (7.5 mM; pH 4.31), bromhexine (0.1%; pH 4.68), dehydrocholic acid (5%; pH 7.45), and sodium citrate (75 mM; pH 7.23) solutions. Protein plugs in choledochal cysts are dissolved in acidic and basic solutions, which may eliminate longitudinal electrostatic interactions of the lithostathine protofibrils.

A new approach to study cadmium complexes with oxalic acid in soil solution.

PubMed

Dytrtová, Jana Jaklová; Jakl, Michal; Sestáková, Ivana; Zins, Emilie-Laure; Schröder, Detlef; Navrátil, Tomáš

2011-05-05

This study presents a new analytical approach for the determination of heavy metals complexed to low-molecular-weight-organic acids in soil solutions, which combines the sensitivity of differential pulse anodic stripping voltammetry (DPASV) with the molecular insight gained by electrospray ionization mass spectrometry (ESI-MS). The combination of these analytical methods allows the investigation of such complexes in complex matrixes. On the voltammograms of the soil solutions, in addition to the expected complexes of oxalic acid with cadmium and lead, respectively, also peaks belonging to mixed complexes of cadmium, lead, and oxalic acid (OAH(2)) were observed. In order to verify the possible formation of complexes with OAH(2), aqueous solutions of OAH(2) with traces of Cd(II) were investigated as model systems. Signals corresponding to several distinct molecular complexes between cadmium and oxalic acid were detected in the model solutions using negative-ion ESI-MS, which follow the general formula [Cd(n)(X,Y)((2n+1))](-), where n is the number of cadmium atoms, X=Cl(-), and Y=OAH(-). Some of these complexes were also identified in the ESI mass spectra taken from the soil solutions. Copyright © 2011 Elsevier B.V. All rights reserved.

Dissolution of Simulated and Radioactive Savannah River Site High-Level Waste Sludges with Oxalic Acid & Citric Acid Solutions

DOE Office of Scientific and Technical Information (OSTI.GOV)

STALLINGS, MARY

This report presents findings from tests investigating the dissolution of simulated and radioactive Savannah River Site sludges with 4 per cent oxalic acid and mixtures of oxalic and citric acid previously recommended by a Russian team from the Khlopin Radium Institute and the Mining and Chemical Combine (MCC). Testing also included characterization of the simulated and radioactive waste sludges. Testing results showed the following: Dissolution of simulated HM and PUREX sludges with oxalic and citric acid mixtures at SRTC confirmed general trends reported previously by Russian testing. Unlike the previous Russian testing six sequential contacts of a mixture of oxalicmore » acid citric acids at a 2:1 ratio (v/w) of acid to sludge did not produce complete dissolution of simulated HM and PUREX sludges. We observed that increased sludge dissolution occurred at a higher acid to sludge ratio, 50:1 (v/w), compared to the recommended ratio of 2:1 (v/w). We observed much lower dissolution of aluminum in a simulated HM sludge by sodium hydroxide leaching. We attribute the low aluminum dissolution in caustic to the high fraction of boehmite present in the simulated sludge. Dissolution of HLW sludges with 4 per cent oxalic acid and oxalic/citric acid followed general trends observed with simulated sludges. The limited testing suggests that a mixture of oxalic and citric acids is more efficient for dissolving HM and PUREX sludges and provides a more homogeneous dissolution of HM sludge than oxalic acid alone. Dissolution of HLW sludges in oxalic and oxalic/citric acid mixtures produced residual sludge solids that measured at higher neutron poison to equivalent 235U weight ratios than that in the untreated sludge solids. This finding suggests that residual solids do not present an increased nuclear criticality safety risk. Generally the neutron poison to equivalent 235U weight ratios of the acid solutions containing dissolved sludge components are lower than those in the

Evidence for the absence of the terminal adenine nucleotide at the amino acid-acceptor end of transfer ribonucleic acid in non-lactating bovine mammary gland and its inhibitory effect on the aminoacylation of rat liver transfer ribonucleic acid

PubMed Central

Herrington, M. D.; Hawtrey, A. O.

1970-01-01

1. tRNA isolated from non-lactating bovine mammary gland competitively inhibits the formation of aminoacyl-tRNA in the rat liver system. 2. Non-lactating bovine mammary gland tRNA and twice-pyrophosphorolysed rat liver tRNA are unable to accept amino acids in a reaction catalysed by aminoacyl-tRNA synthetases from either rat liver or bovine mammary gland. Deacylated rat liver tRNA can however be aminoacylated in the presence of either enzyme. 3. Bovine mammary gland tRNA lacks the terminal adenine nucleotide at the 3′-terminus amino acid acceptor end, which can be replaced by incubation in the presence of rat liver nucleotide-incorporating enzyme, ATP and CTP. 4. The enzymically modified bovine tRNA (tRNApCpCpA) can bind labelled amino acids to form aminoacyl-tRNA, which can then transfer its labelled amino acids to growing polypeptide chains on ribosomes. 5. Molecules of rat liver tRNA or bovine mammary gland tRNA that lack the terminal adenine nucleotide or the terminal cytosine and adenine nucleotides inhibit the aminoacylation of normal rat liver tRNA to varying degrees. tRNA molecules lacking the terminal −pCpCpA nucleotide sequence exhibit the major inhibitory effect. 6. The enzyme fraction from bovine mammary gland corresponding to that containing the nucleotide-incorporating enzyme in rat liver is unable to catalyse the incorporation of cytosine and adenine nucleotides in pyrophosphorolysed rat liver tRNA and deacylated bovine tRNA. This fraction also markedly inhibits the action of the rat liver nucleotide-incorporating enzyme. PMID:5435687

Improvement of DNA adenylation using T4 DNA ligase with a template strand and a strategically mismatched acceptor strand

PubMed Central

Patel, Maha P.; Baum, Dana A.; Silverman, Scott K.

2008-01-01

DNA with a 5′-adenylpyrophosphoryl cap (5′-adenylated DNA; AppDNA) is an activated form of DNA that is the biochemical intermediate of the reactions catalyzed by DNA ligase, RNA ligase, polynucleotide kinase, and other nucleic acid modifying enzymes. 5′-Adenylated DNA is also useful for in vitro selection experiments. Efficient preparation of 5′-adenylated DNA is therefore desirable for several biochemical applications. Here we have developed a DNA adenylation procedure that uses T4 DNA ligase and is more reliable than a previously reported approach that used the 5′-phosphorylated donor DNA substrate to be adenylated, a DNA template, and ATP but no acceptor strand. Our improved DNA adenylation procedure uses the above components as well as an acceptor strand that has a strategically chosen C-T acceptor-template mismatch directly adjacent to the adenylation site. This mismatch permits adenylation of the donor DNA substrate but largely suppresses subsequent ligation of the donor with the acceptor, as assayed on nine different DNA substrates that collectively have all four DNA nucleotides represented at each of the first two positions. The new DNA adenylation procedure is successful using either laboratory-prepared or commercial T4 DNA ligase and works well on the preparative (2 nmol) scale for all nine of the test DNA substrates. PMID:18022669

Investigation on solubility of hydroxy dibasic acids in alkanolamine solutions

NASA Astrophysics Data System (ADS)

Du, M.

2017-12-01

Solubilities of three hydroxy dibasic (adipic, suberic, and sebacic) acids in alkanolamine solutions were measured within the 30-90℃ temperature range. It is found that solubility of these acids sharply grows with temperature and concentration of alkanolamine solvent. In addition, the study substantiates the adjustment of pH to optimize the CO2 absorption and desorption processes. The precipitation of added acids from alkanolamine solvents by cooling is found to be quite problematic, which makes the recovery of residual acids from lean alkanolamine solvents non-feasible and requires the application of alternative methods.

Improved method for extracting lanthanides and actinides from acid solutions

DOEpatents

Horwitz, E.P.; Kalina, D.G.; Kaplan, L.; Mason, G.W.

1983-07-26

A process for the recovery of actinide and lanthanide values from aqueous acidic solutions uses a new series of neutral bi-functional extractants, the alkyl(phenyl)-N,N-dialkylcarbamoylmethylphosphine oxides. The process is suitable for the separation of actinide and lanthanide values from fission product values found together in high-level nuclear reprocessing waste solutions.

In situ synthesis, photometric and spectroscopic studies of chelating system during the 1,4,7,10,13,16-hexaoxacyclooctadecane charge transfer reaction with different acceptors

NASA Astrophysics Data System (ADS)

Hossan, Aisha S. M.; Abou-Melha, Hanaa M.; Refat, Moamen S.

2011-08-01

Electron donor acceptor complexes (EDA) of the 1,4,7,10,13,16-hexaoxacyclooctadecane (18-crown-6) as a rich donor were spectrophotometrically discussed and synthesized in solid form according the interactions with different nine of usual π-acceptors like 2,3,5,6-tetrachlorocyclohexa-2,5-diene-1,4-dione (p-chloranil; p-CHL), tetrachloro-1,2-benzoquinone (o-chloranil; o-CHL), 2,3-dichloro-5,6-dicyano-1,4-benzoquinone (DDQ), tetracyanoquinodimethane (TCNQ), 2,6-dichloroquinone-4-chloroimide (DCQ), 2,6-dibromoquinone-4-chloroimide (DBQ), 2,5-dichloro-3,6-dihydroxy-1,4-benzoquinone (chloranilic acid; CLA), N-bromosuccinimide (NBS), 2,4,6-trinitrophenol (picric acid; PA). Spectroscopic and physical data such as formation constant ( KCT), molar extinction coefficient ( ɛCT), standard free energy (Δ G°), oscillator strength ( f), transition dipole moment ( μ), resonance energy ( RN) and ionization potential ( Ip) were estimated in chloroform or methanol at 25 °C. Based on the elemental analysis and photometric titrations the CT-complexes were formed indicated the formation of 1:1 charge-transfer complexes for the o-CHL, TCNQ, DCQ, DBQ and NBS acceptors but 1:3 ratio for p-CHL, DDQ, CLA and PA, respectively. The charge-transfer interactions were interpretative according to the formation of dative ion pairs [18C6 rad +, A rad -], where A is acceptor. All of the resulting charge transfer complexes were isolated in amorphous form and the complexes formations on IR and 1H NMR spectra were discussed.

Speciation of platinum(IV) in nitric acid solutions.

PubMed

Vasilchenko, Danila; Tkachev, Sergey; Baidina, Iraida; Korenev, Sergey

2013-09-16

The speciation of platinum(IV) ions in nitric acid (6-15.8 M) solutions of H2[Pt(OH)6] has been studied by (195)Pt NMR and Raman spectroscopy. Series of aqua-hydroxo-nitrato complexes [Pt(L)(x)(NO3)(6-x)] (L = H2O or OH(-); x = 0, ..., 6) were found to exist in such solutions. The pair additivity model of chemical shifts and statistical theory were used to assign signals in NMR spectra to particular [Pt(L)(x)(NO3)(6-x)] species. Mononuclear hexanitratoplatinates(IV) have been isolated in solid state in substantial yield as pyridinium salt (PyH)2[Pt(NO3)6] and characterized by single-crystal X-ray diffraction. Aging of the platinum nitric acid solutions for more than 5-6 h results in oligomerization of [Pt(L)(x)(NO3)(6-x)] species and the formation of oligonuclear aqua-hydroxo-nitrato complexes with OH(-) and NO3(-) bridging ligands. Oligomeric platinum(IV) complexes with two and four nuclei were unambiguously detected by NMR on (195)Pt -enriched samples. Oligomers with even higher nuclearity were also detected. Dimeric anions [Pt2(μ-OH)2(NO3)8](2-) have been isolated as single crystals of tetramethylammonium salt and characterized by X-ray diffraction.

Extraction of steroidal glucosiduronic acids from aqueous solutions by anionic liquid ion-exchangers

PubMed Central

Mattox, Vernon R.; Litwiller, Robert D.; Goodrich, June E.

1972-01-01

A pilot study on the extraction of three steroidal glucosiduronic acids from water into organic solutions of liquid ion-exchangers is reported. A single extraction of a 0.5mm aqueous solution of either 11-deoxycorticosterone 21-glucosiduronic acid or cortisone 21-glucosiduronic acid with 0.1m-tetraheptylammonium chloride in chloroform took more than 99% of the conjugate into the organic phase; under the same conditions, the very polar conjugate, β-cortol 3-glucosiduronic acid, was extracted to the extent of 43%. The presence of a small amount of chloride, acetate, or sulphate ion in the aqueous phase inhibited extraction, but making the aqueous phase 4.0m with ammonium sulphate promoted extraction strongly. An increase in the concentration of ion-exchanger in the organic phase also promoted extraction. The amount of cortisone 21-glucosiduronic acid extracted by tetraheptylammonium chloride over the pH range of 3.9 to 10.7 was essentially constant. Chloroform solutions of a tertiary, a secondary, or a primary amine hydrochloride also will extract cortisone 21-glucosiduronic acid from water. The various liquid ion exchangers will extract steroidal glucosiduronic acid methyl esters from water into chloroform, although less completely than the corresponding free acids. The extraction of the glucosiduronic acids from water by tetraheptylammonium chloride occurs by an ion-exchange process; extraction of the esters does not involve ion exchange. PMID:5075264

Synthesis, spectral and thermal studies of the newly hydrogen bonded charge transfer complex of o-phenylenediamine with pi acceptor picric acid.

PubMed

Khan, Ishaat M; Ahmad, Afaq

2010-10-01

Newly proton or charge transfer complex [(OPDH)(+)(PA)(-)] was synthesized by the reaction of the donor, o-phenylenediamine (OPD) with acceptor, 2,4,6-trinitrophenol (PAH). The chemical reaction has occurred via strong hydrogen bonding followed by migration of proton from acceptor to donor. UV-vis, (1)H NMR and FTIR spectra, in addition to the thermal and elemental analysis were used to confirm the proposed occurrence of the chemical reaction and to investigate the newly synthesized solid CT complex. The stoichiometry of the CT complex was found to be 1:1. The formation constant and molar extinction coefficient of the CT complex were evaluated by the Benesi-Hildebrand equation. Copyright 2010 Elsevier B.V. All rights reserved.

Small molecule BODIPY dyes as non-fullerene acceptors in bulk heterojunction organic photovoltaics.

PubMed

Poe, Ambata M; Della Pelle, Andrea M; Subrahmanyam, Ayyagari V; White, William; Wantz, Guillaume; Thayumanavan, S

2014-03-18

A series of acceptor-donor-acceptor molecules containing terminal BODIPY moieties conjugated through the meso position were synthesized. Deep LUMO energy levels and good visible absorption led to their use as acceptors in bulk heterojunction solar cells. Inverted devices were fabricated, reaching efficiencies as high as 1.51%.

DYNAMIC CONDUCTIVITY MEASUREMENTS IN HUMIC AND FULVIC ACID SOLUTIONS. (R828158)

EPA Science Inventory

Conductivity changes of dilute aqueous humic and fulvic acids solutions were monitored after the addition of small quantities of Cu, Cd, Pb, and Zn. The solutions were stirred at a constant and reproducible rate, and measurements proceeded until stable conductivities were atta...

Difference between resistance degradation of fixed valence acceptor (Mg) and variable valence acceptor (Mn)-doped BaTiO3 ceramics

NASA Astrophysics Data System (ADS)

Yoon, Seok-Hyun; Randall, Clive A.; Hur, Kang-Heon

2010-09-01

The difference in the resistance degradation behavior was investigated between fixed valence acceptor (Mg) and the variable valence acceptor (Mn)-doped BaTiO3 ceramics with an increase of each acceptor concentration. Coarse-grained specimens with uniform grain sizes and different acceptor concentrations were prepared. In the case of Mg-doped BaTiO3, the time to degradation systematically decreased with the increase in Mg concentration. In contrast, there is a systematically increased time to degradation with the increase in Mn concentration in Mn-doped BaTiO3. The fast degradation by the increase in Mg concentration directly corresponded to an increase in the Warburg impedance and ionic transference number (tion) associated with an increase in oxygen vacancy concentration ([VO••]). On the other hand, no distinct Warburg impedance or ionic conduction contribution could be observed with the increase in Mn concentration. It is supposed that the increase in [VO••] is negligible in spite of the increase in acceptor Mn concentration, when it is compared to Mg-doped BaTiO3. The much lower [VO••] and more dominant electron/hole trapping effect due to multivalence nature of Mn are supposed to cause such a contrary degradation behavior between Mg and Mn-doped BaTiO3. Reoxidation in a slightly reducing atmosphere (N2) showed better resistance to degradation behavior than in a oxidizing air atmosphere in both Mg and Mn-doped BaTiO3, which is anticipated to be an increase in the electron/hole trapping sites. All these behaviors could be explained by the low temperature defect chemical model that shows difference in the defect structure between Mg and Mn-doped BaTiO3, and its dependence on the oxygen partial pressure (pO2) during reoxidation and cooling. Not only the [VO••], but also the density of electron/hole trap sites, are believed to be crucial in controlling resistance degradation.

Alkaline earth cation extraction from acid solution

DOEpatents

Dietz, Mark; Horwitz, E. Philip

2003-01-01

An extractant medium for extracting alkaline earth cations from an aqueous acidic sample solution is described as are a method and apparatus for using the same. The separation medium is free of diluent, free-flowing and particulate, and comprises a Crown ether that is a 4,4'(5')[C.sub.4 -C.sub.8 -alkylcyclohexano]18-Crown-6 dispersed on an inert substrate material.

Non-fullerene acceptors for organic solar cells

NASA Astrophysics Data System (ADS)

Yan, Cenqi; Barlow, Stephen; Wang, Zhaohui; Yan, He; Jen, Alex K.-Y.; Marder, Seth R.; Zhan, Xiaowei

2018-03-01

Non-fullerene acceptors (NFAs) are currently a major focus of research in the development of bulk-heterojunction organic solar cells (OSCs). In contrast to the widely used fullerene acceptors (FAs), the optical properties and electronic energy levels of NFAs can be readily tuned. NFA-based OSCs can also achieve greater thermal stability and photochemical stability, as well as longer device lifetimes, than their FA-based counterparts. Historically, the performance of NFA OSCs has lagged behind that of fullerene devices. However, recent developments have led to a rapid increase in power conversion efficiencies for NFA OSCs, with values now exceeding 13%, demonstrating the viability of using NFAs to replace FAs in next-generation high-performance OSCs. This Review discusses the important work that has led to this remarkable progress, focusing on the two most promising NFA classes to date: rylene diimide-based materials and materials based on fused aromatic cores with strong electron-accepting end groups. The key structure-property relationships, donor-acceptor matching criteria and aspects of device physics are discussed. Finally, we consider the remaining challenges and promising future directions for the NFA OSCs field.

[Effects of choledochal perfusion with biliary acid solutions on activity of the sphincter of Oddi (author's transl)].

PubMed

Bevilacqua, R G; Margarido, N F; Soares, L A; Mansur, R; Koch, V; Gonçalves, E L

1979-06-01

The changes of sphincter of Oddi's resistance, induced by choledochal perfusion of conjugated (taurocolic) and non-conjugated (colic) biliary acid solutions, in anesthetized dogs, were studied. The perfusions were made at a constant flow and intracholedochal pressures were registered. The mean number of contractions per minute, the mean maximal pressures and the mean minimal pressures in each study periods were analysed. The choledochal perfusion with the biliary acids solutions induced a slight but significative increase in sphincteric resistance. After 15 minutes, the perfusion with colic acid solution induced maximal pressures significantly more elevated than the ones observed with taurocolic acid solution. The non-conjugated solution induced a pressure tracing significantly distinct from the tracing observed with the conjugated acid solution. No changes in resistance were observed with a 2% NaCl solution. This implies that the observed changes in resistance were not related to osmotic stimulation of the sphincter of Oddi.

An overview of molecular acceptors for organic solar cells

NASA Astrophysics Data System (ADS)

Hudhomme, Piétrick

2013-07-01

Organic solar cells (OSCs) have gained serious attention during the last decade and are now considered as one of the future photovoltaic technologies for low-cost power production. The first dream of attaining 10% of power coefficient efficiency has now become a reality thanks to the development of new materials and an impressive work achieved to understand, control and optimize structure and morphology of the device. But most of the effort devoted to the development of new materials concerned the optimization of the donor material, with less attention for acceptors which to date remain dominated by fullerenes and their derivatives. This short review presents the progress in the use of non-fullerene small molecules and fullerene-based acceptors with the aim of evaluating the challenge for the next generation of acceptors in organic photovoltaics.

Simulation study on the effects of chemical structure and molecular size on the acceptor strength in poly(3-hexylthiophene)-based copolymer with alternating donor and acceptor for photovoltaic applications

NASA Astrophysics Data System (ADS)

Rassamesard, Areefen; Pengpan, Teparksorn

2017-02-01

This research assessed the effects of various chemical structures and molecular sizes on the simulated geometric parameters, electron structures, and spectroscopic properties of single-chain complex alternating donor-acceptor (D-A) monomers and copolymers that are intended for use as photoactive layer in a polymer solar cell by using Kohn-Sham density functional theory with B3LYP exchange-correlation functional. The 3-hexylthiophene (3HT) was selected for electron donor, while eight chemicals, namely thiazole (Z), thiadiazole (D), thienopyrazine (TP), thienothiadiazole (TD), benzothiadiazole (BT), thiadiazolothieno-pyrazine (TPD), oxadiazole (OXD) and 5-diphenyl-1,2,4-triazole (TAZ), were employed as electron acceptor functional groups. The torsional angle, bridge bond length, intramolecular charge transfer, energy levels, and molecular orbitals were analyzed. The simulation results reveal that the geometry and electron structure of donor-acceptor monomer and copolymer are significantly impacted by heterocyclic rings, heteroatoms, fused rings, degree of steric hindrance and coplanarity of the acceptor molecular structure. Planar conformation was obtained from the D copolymer, and a pseudo-planar structure with the TD copolymer. The TAZ acceptor exhibited strong steric hindrance due to its bulky structure and non-planarity of its structure. An analysis of the electron structures indicated that the degree of intramolecular electron-withdrawing capability had the rank order TAZ  <  Z  <  D  <  TPD  <  OXD  <  TP  <  BT  <  TD. The TD is indicated as the most effective acceptor among those that were simulated. However, the small energy gaps of TD as well as TPD copolymer indicate that these two copolymers can be used in transparent conducting materials. The copolymer based on BT acceptor exhibited good intramolecular charge transfer and absorbed at 656 nm wavelength which is close to the maximum flux of solar

Dibenzothiophene-Substituted Fullerene Derivative as Electron Acceptor for Polymer Solar Cells.

PubMed

Kim, Hee Un; Park, Jong Baek; Hwang, Do-Hoon

2016-05-01

A new fullerene derivative, [6,6]-dibenzo[b,d]thiophene-C61-butyric acid methyl ester (DBTC61BM) was synthesized from C60 using tosylhydrazone, and used as an electron-acceptor material for poly(3-hexylthiophene) (P3HT)-based organic photovoltaic cells. The synthesized DBTC61BM was used to modify the basic structure of [6,6]-phenyl-C61-butyric acid methyl ester (PC61BM) by replacing the aromatic part with dibenzo[b,d]thiophene. The solubilities of DBTC61BM and PC61BM are similar; they have good solubilities in common organic solvents such as dichloromethane, chloroform, toluene, and 1,2-dichlorobenzene. The Stern-Volmer quenching constant (K(sv)) of DBTC61BM was 7.14 x 10(3) M(-1), and was correlated with the binding affinity between the fluorophore and a quencher. The lowest unoccupied molecular orbital energy level of DBTC61BM was -3.71 eV. The charge-carrier mobility of a P3HT:DBTC61BM blend film was determined using the space-charge-limited current method; the electron mobility value obtained for the P3HT:DBTC61BM blend film was 2.13 x 10(-4) cm2 V(-1) s(-1). Photovoltaic devices were fabricated using P3HT as the electron donor and DBTC61BM as the electron acceptor. Among the fabricated devices, photovoltaic cells with the structure ITO/PEDOT:PSS/P3HT:DBTC61BM/LiF/Al showed the highest power conversion efficiency, namely 3.23%, with an open-circuit voltage of 0.64 V, short-circuit-current density of 8.14 mA cm(-2), and fill factor of 0.59, under AM 1.5 G (100 mW cm(-2)) illumination.

Comparative study of buffered 50% glycolic acid (pH 3.0) + 0.5% salicylic acid solution vs Jessner's solution in patients with acne vulgaris.

PubMed

In Jae, Jeong; Dong Ju, Hyun; Dong Hyun, Kim; Yoon, Moon Soo; Lee, Hee Jung

2017-11-21

Superficial chemical peels are frequently used in acne vulgaris treatment. Although glycolic acid (GA) has been widely used in clinical practice, its pH ranges from 0.08-2.75 and thus should be neutralized after application to avoid burns. To evaluate treatment efficacy and safety of chemical peeling using buffered 50% GA (pH 3.0) + 0.5% salicylic acid (SA) solution that does not need to be neutralized in the treatment of acne vulgaris compared to the conventional peeling using Jessner's solution. We performed a prospective, randomized, evaluator-blind, split-face clinical trial. Twenty patients were randomized by assigning one side of each patient's face to receive a 50% GA (pH 3.0) + 0.5% SA peel (GA side) and the other side to receive the Jessner's solution (Jessner's solution side). All patients underwent 2 sessions of treatment spaced 2 weeks apart. Lesion count, acne severity, subjective efficacy assessment, and side effects were evaluated. The total lesion count was significantly reduced for the GA and Jessner's solution sides (P < .001). However, there was no significant difference in the total lesion count, acne severity, or subjective efficacy assessment between the 2 sides (P > .05). The GA side had fewer side effects than the Jessner's solution side. The results of this study suggest that chemical peeling using the 50% GA (pH 3.0) + 0.5% SA solution can be as effective and convenient as the conventional peeling using Jessner's solution in the treatment of acne vulgaris and may show fewer adverse events than the conventional peeling. © 2017 Wiley Periodicals, Inc.

Reactive solute transport in acidic streams

USGS Publications Warehouse

Broshears, R.E.

1996-01-01

Spatial and temporal profiles of Ph and concentrations of toxic metals in streams affected by acid mine drainage are the result of the interplay of physical and biogeochemical processes. This paper describes a reactive solute transport model that provides a physically and thermodynamically quantitative interpretation of these profiles. The model combines a transport module that includes advection-dispersion and transient storage with a geochemical speciation module based on MINTEQA2. Input to the model includes stream hydrologic properties derived from tracer-dilution experiments, headwater and lateral inflow concentrations analyzed in field samples, and a thermodynamic database. Simulations reproduced the general features of steady-state patterns of observed pH and concentrations of aluminum and sulfate in St. Kevin Gulch, an acid mine drainage stream near Leadville, Colorado. These patterns were altered temporarily by injection of sodium carbonate into the stream. A transient simulation reproduced the observed effects of the base injection.

Nonclinical safety evaluation of boric acid and a novel borate-buffered contact lens multi-purpose solution, Biotrue™ multi-purpose solution.

PubMed

Lehmann, David M; Cavet, Megan E; Richardson, Mary E

2010-12-01

Multipurpose solutions (MPS) often contain low concentrations of boric acid as a buffering agent. Limited published literature has suggested that boric acid and borate-buffered MPS may alter the corneal epithelium; an effect attributed to cytotoxicity induced by boric acid. However, this claim has not been substantiated. We investigated the effect of treating cells with relevant concentrations of boric acid using two cytotoxicity assays, and also assessed the impact of boric acid on corneal epithelial barrier function by measuring TEER and immunostaining for tight junction protein ZO-1 in human corneal epithelial cells. Boric acid was also assessed in an in vivo ocular model when administered for 28 days. Additionally, we evaluated Biotrue multi-purpose solution, a novel borate-buffered MPS, alone and with contact lenses for ocular compatibility in vitro and in vivo. Boric acid passed both cytotoxicity assays and did not alter ZO-1 distribution or corneal TEER. Furthermore, boric acid was well-tolerated on-eye following repeated administration in a rabbit model. Finally, Biotrue multi-purpose solution demonstrated good ocular biocompatibility both in vitro and in vivo. This MPS was not cytotoxic and was compatible with the eye when administered alone and when evaluated with contact lenses. We demonstrate that boric acid and a borate-buffered MPS is compatible with the ocular environment. Our findings provide evidence that ocular effects reported for some borate-buffered MPS may be incorrectly attributed to boric acid and are more likely a function of the unique combination of ingredients in the MPS formulation tested. Copyright © 2010 British Contact Lens Association. Published by Elsevier Ltd. All rights reserved.

Solution properties and taste behavior of lactose monohydrate in aqueous ascorbic acid solutions at different temperatures: Volumetric and rheological approach.

PubMed

Sarkar, Abhijit; Sinha, Biswajit

2016-11-15

The densities and viscosities of lactose monohydrate in aqueous ascorbic acid solutions with several molal concentrations m=(0.00-0.08)molkg(-1) of ascorbic acid were determined at T=(298.15-318.15)K and pressure p=101kPa. Using experimental data apparent molar volume (ϕV), standard partial molar volume (ϕV(0)), the slope (SV(∗)), apparent specific volumes (ϕVsp), standard isobaric partial molar expansibility (ϕE(0)) and its temperature dependence [Formula: see text] the viscosity B-coefficient and solvation number (Sn) were determined. Viscosity B-coefficients were further employed to obtain the free energies of activation of viscous flow per mole of the solvents (Δμ1(0≠)) and of the solute (Δμ2(0≠)). Effects of molality, solute structure and temperature and taste behavior were analyzed in terms of solute-solute and solute-solvent interactions; results revealed that the solutions are characterized predominantly by solute-solvent interactions and lactose monohydrate behaves as a long-range structure maker. Copyright © 2016 Elsevier Ltd. All rights reserved.

An Organic Puzzle Using Meldrum's Acid

NASA Astrophysics Data System (ADS)

Crouch, R. David; Holden, Michael S.

2002-04-01

Meldrum's acid or 2,2-dimethyl-1,3-dioxane-4,6-dione undergoes a Knoevenagel condensation with formaldehyde to form an active Michael acceptor for a second molecule of Meldrum's acid. The structure of the resulting product is determined by correlation of the products of possible reactions of Meldrum's acid and formaldehyde with the NMR spectrum of the product.

Interaction of Ethyl Alcohol Vapor with Sulfuric Acid Solutions

NASA Technical Reports Server (NTRS)

Leu, Ming-Taun

2006-01-01

We investigated the uptake of ethyl alcohol (ethanol) vapor by sulfuric acid solutions over the range approx.40 to approx.80 wt % H2SO4 and temperatures of 193-273 K. Laboratory studies used a fast flow-tube reactor coupled to an electron-impact ionization mass spectrometer for detection of ethanol and reaction products. The uptake coefficients ((gamma)) were measured and found to vary from 0.019 to 0.072, depending upon the acid composition and temperature. At concentrations greater than approx.70 wt % and in dilute solutions colder than 220 K, the values approached approx.0.07. We also determined the effective solubility constant of ethanol in approx.40 wt % H2SO4 in the temperature range 203-223 K. The potential implications to the budget of ethanol in the global troposphere are briefly discussed.

Electro-driven extraction of polar compounds using agarose gel as a new membrane: Determination of amino acids in fruit juice and human plasma samples.

PubMed

Sedehi, Samira; Tabani, Hadi; Nojavan, Saeed

2018-03-01

In this work, polypropylene hollow fiber was replaced by agarose gel in conventional electro membrane extraction (EME) to develop a novel approach. The proposed EME method was then employed to extract two amino acids (tyrosine and phenylalanine) as model polar analytes, followed by HPLC-UV. The method showed acceptable results under optimized conditions. This green methodology outperformed conventional EME, and required neither organic solvents nor carriers. The effective parameters such as the pH values of the acceptor and the donor solutions, the thickness and pH of the gel, the extraction voltage, the stirring rate, and the extraction time were optimized. Under the optimized conditions (acceptor solution pH: 1.5; donor solution pH: 2.5; agarose gel thickness: 7mm; agarose gel pH: 1.5; stirring rate of the sample solution: 1000rpm; extraction potential: 40V; and extraction time: 15min), the limits of detection and quantification were 7.5ngmL -1 and 25ngmL -1 , respectively. The extraction recoveries were between 56.6% and 85.0%, and the calibration curves were linear with correlation coefficients above 0.996 over a concentration range of 25.0-1000.0ngmL -1 for both amino acids. The intra- and inter-day precisions were in the range of 5.5-12.5%, and relative errors were smaller than 12.0%. Finally, the optimized method was successfully applied to preconcentrate, clean up, and quantify amino acids in watermelon and grapefruit juices as well as a plasma sample, and acceptable relative recoveries in the range of 53.9-84.0% were obtained. Copyright © 2017 Elsevier B.V. All rights reserved.

Trapping proton transfer intermediates in the disordered hydrogen-bonded network of cryogenic hydrofluoric acid solutions.

PubMed

Ayotte, Patrick; Plessis, Sylvain; Marchand, Patrick

2008-08-28

A molecular-level description of the structural and dynamical aspects that are responsible for the weak acid behaviour of dilute hydrofluoric acid solutions and their unusual increased acidity at near equimolar concentrations continues to elude us. We address this problem by reporting reflection-absorption infrared spectra (RAIRS) of cryogenic HF-H(2)O binary mixtures at various compositions prepared as nanoscopic films using molecular beam techniques. Optical constants for these cryogenic solutions [n(omega) and k(omega)] are obtained by iteratively solving Fresnel equations for stratified media. Modeling of the experimental RAIRS spectra allow for a quantitative interpretation of the complex interplay between multiple reflections, optical interference and absorption effects. The evolution of the strong absorption features in the intermediate 1000-3000 cm(-1) range with increasing HF concentration reveals the presence of various ionic dissociation intermediates that are trapped in the disordered H-bonded network of cryogenic hydrofluoric acid solutions. Our findings are discussed in light of the conventional interpretation of why hydrofluoric acid is a weak acid revealing molecular-level details of the mechanism for HF ionization that may be relevant to analogous elementary processes involved in the ionization of weak acids in aqueous solutions.

Click and chemically triggered declick reactions through reversible amine and thiol coupling via a conjugate acceptor

NASA Astrophysics Data System (ADS)

Diehl, Katharine L.; Kolesnichenko, Igor V.; Robotham, Scott A.; Bachman, J. Logan; Zhong, Ye; Brodbelt, Jennifer S.; Anslyn, Eric V.

2016-10-01

The coupling and decoupling of molecular units is a fundamental undertaking of organic chemistry. Herein we report the use of a very simple conjugate acceptor, derived from Meldrum's acid, for the sequential ‘clicking’ together of an amine and a thiol in aqueous conditions at neutral pH. Subsequently, this linkage can be ‘declicked’ by a chemical trigger to release the original amine and thiol undisturbed. The reactivity differs from that of other crosslinking agents because the selectivity for sequential functionalization derives from an altering of the electrophilicity of the conjugate acceptor on the addition of the amine. We describe the use of the procedure to modify proteins, create multicomponent libraries and synthesize oligomers, all of which can be declicked to their starting components in a controlled fashion when desired. Owing to the mild reaction conditions and ease of use in a variety of applications, the method is predicted to have wide utility.

Influence of D-Penicillamine on the Viscosity of Hyaluronic Acid Solutions

NASA Astrophysics Data System (ADS)

Liang, Jing; Krause, Wendy E.; Colby, Ralph H.

2006-03-01

Polyelectrolyte hyaluronic acid (HA, hyaluronan) is an important component in synovial fluid. Its presence results in highly viscoelastic solutions with excellent lubricating and shock-absorbing properties. In comparison to healthy synovial fluid, diseased fluid has a reduced viscosity. In osteoarthritis this reduction in viscosity results from a decline in both the molecular weight and concentration of hyaluronic acid HA. Initial results indicate that D-penicillamine affects the rheology of bovine synovial fluid, a model synovial fluid solution, and its components, including HA. In order to understand how D-penicillamine modifies the viscosity of these solutions, the rheological properties of sodium hyaluronate (NaHA) in phosphate-buffered saline (PBS) with D-penicillamine were studied as function of time, D-penicillamine concentration (0 -- 0.01 M), and storage conditions. Penicillamine has a complex, time dependent effect on the viscosity of NaHA solutions---reducing the zero shear rate viscosity of a 3 mg/mL NaHA in PBS by ca. 40% after 44 days.

Isotherm-Based Thermodynamic Models for Solute Activities of Organic Acids with Consideration of Partial Dissociation.

PubMed

Nandy, Lucy; Ohm, Peter B; Dutcher, Cari S

2016-06-23

Organic acids make up a significant fraction of the organic mass in atmospheric aerosol particles. The calculation of gas-liquid-solid equilibrium partitioning of the organic acid is therefore critical for accurate determination of atmospheric aerosol physicochemical properties and processes such as new particle formation and activation to cloud condensation nuclei. Previously, an adsorption isotherm-based statistical thermodynamic model was developed for capturing solute concentration-activity relationships for multicomponent aqueous solutions over the entire concentration range (Dutcher et al. J. Phys. Chem. C/A 2011, 2012, 2013), with model parameters for energies of adsorption successfully related to dipole-dipole electrostatic forces in solute-solvent and solvent-solvent interactions for both electrolytes and organics (Ohm et al. J. Phys. Chem. A 2015). However, careful attention is needed for weakly dissociating semivolatile organic acids. Dicarboxylic acids, such as malonic acid and glutaric acid are treated here as a mixture of nondissociated organic solute (HA) and dissociated solute (H(+) + A(-)). It was found that the apparent dissociation was greater than that predicted by known dissociation constants alone, emphasizing the effect of dissociation on osmotic and activity coefficient predictions. To avoid additional parametrization from the mixture approach, an expression was used to relate the Debye-Hückel hard-core collision diameter to the adjustable solute-solvent intermolecular distance. An improved reference state treatment for electrolyte-organic aqueous mixtures, such as that observed here with partial dissociation, has also been proposed. This work results in predictive correlations for estimation of organic acid and water activities for which there is little or no activity data.

Effect of sodium metabisulfite on hydrogen peroxide production in light-exposed pediatric parenteral amino acid solutions.

PubMed

Brawley, V; Bhatia, J; Karp, W B

1998-06-15

The effect of sodium metabisulfite (MBS) on hydrogen peroxide (HP) production in model and commercial amino acid solutions exposed to phototherapy light was studied. Model and commercial pediatric amino acid solutions were prepared such that the amino acid concentration was 1%. MBS concentration, riboflavin concentration, and duration of exposure to phototherapy light were varied to determine the effect on HP production. Control solutions were kept in the dark. HP production was assayed in the model amino acid solutions by using potassium iodide in the presence of ammonium molybdate. In all experiments, HP production was measured at 360 nm in the presence and absence of catalase. In light-exposed solutions, HP production increased linearly for several hours and reached a plateau by eight hours. A mean maximum of 940 microM was produced (data pooled for all solutions). No detectable HP was generated in the solutions kept in the dark. After two hours of light exposure, it was necessary to add at least 10 times more MBS than is typically found in commercial total parenteral nutrient solutions to scavenge all the HP produced. An average of up to 940 microM of HP was produced in model and commercial pediatric parenteral 1% amino acid solutions in the presence of phototherapy light and clinically relevant concentrations of riboflavin and MBS. Light exposure decreased the antioxidant effect of MBS.

Solution-based electrical doping of semiconducting polymer films over a limited depth

NASA Astrophysics Data System (ADS)

Kolesov, Vladimir A.; Fuentes-Hernandez, Canek; Chou, Wen-Fang; Aizawa, Naoya; Larrain, Felipe A.; Wang, Ming; Perrotta, Alberto; Choi, Sangmoo; Graham, Samuel; Bazan, Guillermo C.; Nguyen, Thuc-Quyen; Marder, Seth R.; Kippelen, Bernard

2017-04-01

Solution-based electrical doping protocols may allow more versatility in the design of organic electronic devices; yet, controlling the diffusion of dopants in organic semiconductors and their stability has proven challenging. Here we present a solution-based approach for electrical p-doping of films of donor conjugated organic semiconductors and their blends with acceptors over a limited depth with a decay constant of 10-20 nm by post-process immersion into a polyoxometalate solution (phosphomolybdic acid, PMA) in nitromethane. PMA-doped films show increased electrical conductivity and work function, reduced solubility in the processing solvent, and improved photo-oxidative stability in air. This approach is applicable to a variety of organic semiconductors used in photovoltaics and field-effect transistors. PMA doping over a limited depth of bulk heterojunction polymeric films, in which amine-containing polymers were mixed in the solution used for film formation, enables single-layer organic photovoltaic devices, processed at room temperature, with power conversion efficiencies up to 5.9 +/- 0.2% and stable performance on shelf-lifetime studies at 60 °C for at least 280 h.

A survey of acceptor dopants for β-Ga2O3

NASA Astrophysics Data System (ADS)

Lyons, John L.

2018-05-01

With a wide band gap, high critical breakdown voltage and commercially available substrates, Ga2O3 is a promising material for next-generation power electronics. Like most wide-band-gap semiconductors, obtaining better control over its electrical conductivity is critically important, but has proven difficult to achieve. Although efficient p-type doping in Ga2O3 is not expected, since theory and experiment indicate the self-trapping of holes, the full development of this material will require a better understanding of acceptor dopants. Here the properties of group 2, group 5 and group 12 acceptor impurities in β-Ga2O3 are explored using hybrid density functional calculations. All impurities are found to exhibit acceptor transition levels above 1.3 eV. After examining formation energies as a function of chemical potential, Mg (followed closely by Be) is determined to be the most stable acceptor species.

Ultrasound assisted cocrystallization from solution (USSC) containing a non-congruently soluble cocrystal component pair: Caffeine/maleic acid.

PubMed

Aher, Suyog; Dhumal, Ravindra; Mahadik, Kakasaheb; Paradkar, Anant; York, Peter

2010-12-23

Ultrasound assisted solution cocrystallization (USSC) has been studied using a non-congruently soluble pair of caffeine and maleic acid in methanol. USSC was compared with solvent cooling and slurry sonication using different molar ratios of caffeine:maleic acid (1:0.5, 1:1, 1:2, 1:3 and 1:3.5) in solution/slurry. Products were characterized by PXRD and Raman spectroscopy techniques. In USSC trials, the content of cocrystal in the product was observed to increase with increase in amount of maleic acid in solution. Only USSC offered pure caffeine/maleic acid 2:1 cocrystal product when caffeine:maleic acid; 1:3.5 molar ratio was taken in solution. Caffeine/maleic acid 1:1 cocrystal and maleic acid were not obtained in neither of the techniques. Products of solvent cooling and slurry sonication experiments were mixtures of caffeine and caffeine/maleic acid 2:1 cocrystal in varying amounts. In USSC, ultrasound application must have attained simultaneous supersaturation of cocrystal components in solution due to altered supersaturation conditions resulting in cocrystal formation. For this simultaneous attainment of supersaturation, molar ratio of cocrystal components in solution was identified as an important parameter while designing experiments for a non-congruently soluble pair having large solubility difference. Copyright © 2010 Elsevier B.V. All rights reserved.

Michael acceptor containing drugs are a novel class of 5-lipoxygenase inhibitor targeting the surface cysteines C416 and C418.

PubMed

Maucher, Isabelle V; Rühl, Michael; Kretschmer, Simon B M; Hofmann, Bettina; Kühn, Benjamin; Fettel, Jasmin; Vogel, Anja; Flügel, Karsten T; Manolikakes, Georg; Hellmuth, Nadine; Häfner, Ann-Kathrin; Golghalyani, Vahid; Ball, Ann-Katrin; Piesche, Matthias; Matrone, Carmela; Geisslinger, Gerd; Parnham, Michael J; Karas, Michael; Steinhilber, Dieter; Roos, Jessica; Maier, Thorsten J

2017-02-01

Recently, we published that nitro-fatty acids (NFA) are potent electrophilic molecules which inhibit 5-lipoxygenase (5-LO) by interacting catalytically with cysteine residues next to a substrate entry channel. The electrophilicity is derived from an intramolecular Michael acceptor moiety consisting of an electron-withdrawing group in close proximity to a double bond. The potential of the Michael acceptor moiety to interact with functionally relevant cysteines of proteins potentially renders them effective and sustained enzyme activity modulators. We screened a large library of naturally derived and synthetic electrophilic compounds to investigate whether other types of Michael acceptor containing drugs suppress 5-LO enzyme activity. The activity was measured by assessing the effect on the 5-LO product formation of intact human polymorphonuclear leukocytes. We demonstrated that a number of structurally different compounds were suppressive in the activity assays and showed that Michael acceptors of the quinone and nitro-alkene group produced the strongest inhibition of 5-LO product formation. Reactivity with the catalytically relevant cysteines 416 and 418 was confirmed using mutated recombinant 5-LO and mass spectrometric analysis (MALDI-MS). In the present study, we show for the first time that a number of well-recognized naturally occurring or synthetic anti-inflammatory compounds carrying a Michael acceptor, such as thymoquinone (TQ), the paracetamol metabolite NAPQI, the 5-LO inhibitor AA-861, and bardoxolone methyl (also known as RTA 402 or CDDO-methyl ester) are direct covalent 5-LO enzyme inhibitors that target the catalytically relevant cysteines 416 and 418. Copyright © 2016 Elsevier Inc. All rights reserved.

Hybrid coconut seedlings, scholarships, and discount cards for family planning acceptors.

PubMed

Sumarsono

1989-10-01

Having learned from failed family planning (FP) incentive schemes in other countries, Indonesia implemented a reward system designed to popularize FP in the community. In order to overcome cultural opposition to FP, many countries in the 1970s opted to give incentives--money, materials, etc.--to new contraceptive acceptors and the FP workers who successfully recruited them. These countries, which oftentimes spent up to 1/4 of their program budget on incentives, saw rapid increases in the number of new acceptors. The results, however, only reflected a superficial acceptance of FP. When the incentives stopped, the number of acceptors dropped considerably. Recognizing this, the Indonesian government set out to increase FP acceptance by making the small family the norm in the community. And one of the approaches for doing so was a reward system. The goals of the reward program were: 1) to raise awareness of the recognition given to individuals or groups that have accepted FP; 2) to create pride among FP workers and new acceptors; and 3) to generate leadership in the community. Villages with high FP acceptance receive rewards such as deep-wells that provide clean water or income generating projects. Individuals also receive rewards that sometimes include hybrid coconut seedlings which, after 3 years, can yield up to 700 coconuts, which can provide a family with a significant supplemental income. The government also gives scholarships to children of FP acceptors. Also, the president of Indonesia publicly recognized family planning acceptors. In 1989, over 800,000 couples received awards for practicing contraception over the past 5-16 years.

Acceptor Products of Alternansucrase with Gentiobiose

USDA-ARS?s Scientific Manuscript database

In the presence of suitable acceptor molecules, dextransucrase makes a homologous series of oligosaccharides in which the isomers differ by a single glucosyl unit, whereas alternansucrase synthesizes one trisaccharide, two tetrasaccharides, etc. Previously, we showed that alternansucrase only forms...

Improvement of n-caproic acid production with Ruminococcaceae bacterium CPB6: selection of electron acceptors and carbon sources and optimization of the culture medium.

PubMed

Wang, Han; Li, Xiangzhen; Wang, Yi; Tao, Yong; Lu, Shaowen; Zhu, Xiaoyu; Li, Daping

2018-06-25

Global energy and resource shortages make it necessary to quest for renewable resources. n-Caproic acid (CA) production based on carboxylate platform by anaerobic fermentation is booming. Recently, a novel Ruminococcaceae bacterium CPB6 is shown to be a potential biotransformation factory for CA production from lactate-containing wastewater. However, little is known about the effects of different electron acceptors (EAs) on the fermentative products of strain CPB6, as well as the optimum medium for CA production. In this study, batch experiments were performed to investigate the fermentative products of strain CPB6 in a lactate medium supplemented with different EAs and sugars. Supplementation of acetate, butyrate and sucrose dramatically increased cell growth and CA production. The addition of propionate or pentanoate resulted in the production of C5 or C7 carboxylic acid, respectively. Further, a Box-Behnken experiment was conducted to optimize the culture medium for CA production. The result indicated that a medium containing 13.30 g/L sucrose, 22.35 g/L lactate and 16.48 g/L butyrate supported high-titer CA production (16.73 g/L) with a maximum productivity of 6.50 g/L/day. This study demonstrated that strain CPB6 could produce C6-C7 carboxylic acids from lactate (as electron donor) with C2-C5 short-chain carboxylic acids (as EAs), but CA (C6 carboxylic acid) was the most major and potential product. Butyrate and sucrose were the most significant EA and carbon source respectively for CA production from lactate by strain CPB6. High titer of CA can be produced from a synthetic substrate containing sucrose, lactate and butyrate. The work provided significant implications for improving CA production in industry-scale.

Highly efficient organic solar cells with improved vertical donor-acceptor compositional gradient via an inverted off-center spinning method

DOE PAGES

Huang, Jiang; Carpenter, Joshua H.; Li, Chang -Zhi; ...

2015-12-02

A novel, yet simple solution fabrication technique to address the trade-off between photocurrent and fill factor in thick bulk heterojunction organic solar cells is described. Lastly, the inverted off-center spinning technique promotes a vertical gradient of the donor–acceptor phase-separated morphology, enabling devices with near 100% internal quantum efficiency and a high power conversion efficiency of 10.95%.

Solution influence on biomolecular equilibria - Nucleic acid base associations

NASA Technical Reports Server (NTRS)

Pohorille, A.; Pratt, L. R.; Burt, S. K.; Macelroy, R. D.

1984-01-01

Various attempts to construct an understanding of the influence of solution environment on biomolecular equilibria at the molecular level using computer simulation are discussed. First, the application of the formal statistical thermodynamic program for investigating biomolecular equilibria in solution is presented, addressing modeling and conceptual simplications such as perturbative methods, long-range interaction approximations, surface thermodynamics, and hydration shell. Then, Monte Carlo calculations on the associations of nucleic acid bases in both polar and nonpolar solvents such as water and carbon tetrachloride are carried out. The solvent contribution to the enthalpy of base association is positive (destabilizing) in both polar and nonpolar solvents while negative enthalpies for stacked complexes are obtained only when the solute-solute in vacuo energy is added to the total energy. The release upon association of solvent molecules from the first hydration layer around a solute to the bulk is accompanied by an increase in solute-solvent energy and decrease in solvent-solvent energy. The techniques presented are expectd to displace less molecular and more heuristic modeling of biomolecular equilibria in solution.

Photoinduced electron transfer in fixed distance chlorophyll-quinone donor-acceptor molecules

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wasielewski, M.R.; Johnson, D.G.; Svec, W.A.

1987-01-01

A series of fixed distance chlorophyll-quinone donor-acceptor molecules have been prepared. The donor consists of either methyl pyropheophorbide a or methyl pyrochlorophyllide a, while the acceptor is either benzoquinone or naphthoquinone. The acceptors are fused to a triptycene spacer group, which in turn is attached to the donors at their vinyl groups. Picosecond transient absorption measurements have been used to identify electron transfer from the lowest excited singlet state of the donor to the acceptor as the mechanism of fluorescence quenching in these molecules. The charge separation rate constants increase from 2 x 10/sup 10/ s/sup -1/ to 4 xmore » 10/sup 11/ s/sup -1/ as the free energy of charge separation increases, while the radical pair recombination rate constants decrease from 1.2 x 10/sup 11/ s/sup -1/ to 2 x 10/sup 9/ s/sup -1/ as the free energy of recombination increases. The resulting total reorganization energy lambda = 0.9 eV.« less

An investigation into the stability and sterility of citric acid solutions used for cough reflex testing.

PubMed

Falconer, James R; Wu, Zimei; Lau, Hugo; Suen, Joanna; Wang, Lucy; Pottinger, Sarah; Lee, Elaine; Alazawi, Nawar; Kallesen, Molly; Gargiulo, Derryn A; Swift, Simon; Svirskis, Darren

2014-10-01

Citric acid is used in cough reflex testing in clinical and research settings to assess reflexive cough in patients at risk of swallowing disorders. To address a lack of knowledge in this area, this study investigated the stability and sterility of citric acid solutions. Triplicate solutions of citric acid (0.8 M) in isotonic saline were stored at 4 ± 2 °C for up to 28 days and analysed by high-performance liquid chromatography. Microbiological sterility of freshly prepared samples and bulk samples previously used for 2 weeks within the hospital was determined using a pour plate technique. Microbial survival in citric acid was determined by inoculating Staphylococcus aureus, Escherichia coli, or Candida albicans into citric acid solution and monitoring the number of colony-forming units/mL over 40 min. Citric acid solutions remained stable at 4 °C for 28 days (98.4 ± 1.8 % remained). The freshly prepared and clinical samples tested were sterile. However, viability studies revealed that citric acid solution allows for the survival of C. albicans but not for S. aureus or E. coli. The microbial survival study showed that citric acid kills S. aureus and E. coli but has no marked effect on C. albicans after 40 min. Citric acid samples at 0.8 M remained stable over the 4-week testing period, with viable microbial cells absent from samples tested. However, C. albicans has the ability to survive in citric acid solution if inadvertently introduced in practice. For this reason, in clinical and research practice it is suggested to use single-use aliquots prepared aseptically which can be stored for up to 28 days at 4 °C.

Understanding the dissolution of α-zein in aqueous ethanol and acetic acid solutions.

PubMed

Li, Yunqi; Li, Ji; Xia, Qiuyang; Zhang, Boce; Wang, Qin; Huang, Qingrong

2012-10-04

Zein is a corn prolamin that has broad industrial applications because of its unique physical properties. Currently, the high cost of extraction and purification, which is directly related to the dispersion of zein in different solvents, is the major bottleneck of the zein industry. Solution behaviors of zein have been studied for a long time. However, the physical nature of zein in different solvents remains unclear. In this study, small-angle X-ray scattering (SAXS), static light scattering (SLS), and rheology were combined to study the structure and protein-solvent interaction of α-zein in both acetic acid and aqueous ethanol solutions. We found that the like-dissolve-like rule, the partial unfolding, and the protonation of zein are all critical to understanding the solution behaviors. Zein holds an elongated conformation (i.e., prolate ellipsoid) in all solutions, as revealed from SAXS data. There is an "aging effect" for zein in aqueous ethanol solutions, as evidenced by the transition of Newtonian rheological profiles for fresh zein solutions to the non-Newtonian shear thinning behavior for zein solutions after storage at room temperature for 24 h. Such shear thinning behavior becomes more pronounced for zein solutions at higher concentrations. The SLS results clearly show that acetic acid is a better solvent to dissolve zein than aqueous ethanol solution, as supported by a more negative second virial coefficient. This is majorly caused by the protonation of the protein, which was further verified by the dissolution of zein in water (a nonsolvent for zein) with the addition of acids.

The kinetics of oxidation of bilirubin and ascorbic acid in solution

NASA Astrophysics Data System (ADS)

Solomonov, A. V.; Rumyantsev, E. V.; Kochergin, B. A.; Antina, E. V.

2012-07-01

The results of a comparative study of the oxidation of bilirubin, ascorbic acid, and their mixture in aqueous solutions under the action of air oxygen and hydrogen peroxide are presented. The observed and true rate constants for the oxidation reactions were determined. It was shown that the oxidation of tetrapyrrole pigment occurred under these conditions bypassing the stage of biliverdin formation to monopyrrole products. Simultaneous oxidation of bilirubin and ascorbic acid was shown to be accompanied by the inhibition of ascorbic acid oxidation by bilirubin, whereas ascorbic acid itself activated the oxidation of bilirubin.

Magnetic resonance studies of the Mg acceptor in thick free-standing and thin-film GaN

NASA Astrophysics Data System (ADS)

Zvanut, Mary Ellen

Mg, the only effective p-type dopant for the nitrides, substitutes for Ga and forms an acceptor with a defect level of about 0.16 eV. The magnetic resonance of such a center should be highly anisotropic, yet early work employing both optically detected magnetic resonance (ODMR) and electron paramagnetic resonance (EPR) spectroscopies revealed a defect with a nearly isotropic g-tensor. The results were attributed to crystal fields caused by compensation and/or strain typical of the heteroepitaxially grown films. The theory was supported by observation of the expected highly anisotropic ODMR signature in homoepitaxially grown films in which dislocation-induced non-uniform strain and compensation are reduced. The talk will review EPR measurements of thin films and describe new work which takes advantage of the recently available thick free-standing GaN:Mg substrates grown by hydride vapor phase epitaxy (HVPE) and high nitrogen pressure solution growth (HNPS). Interestingly, the films and HVPE substrates exhibit characteristically different types of EPR signals, and no EPR response could be induced in the HNPS substrates, with or without illumination. In the heteroepitaxial films, a curious angular dependent line-shape is observed in addition to the nearly isotropic g-tensor characteristic of the Mg-related acceptor. On the other hand, the free-standing HVPE crystals reveal a clear signature of a highly anisotropic shallow acceptor center. Comparison with SIMS measurements implies a direct relation to the Mg impurity, and frequency-dependent EPR studies demonstrate the influence of the anisotropic crystal fields. Overall, the measurements of the thick free-standing crystals show that the Mg acceptor is strongly affected by the local environment. The ODMR was performed by Evan Glaser, NRL and the free-standing Mg-doped HVPE crystals were grown by Jacob Leach, Kyma Tech. The work at UAB is supported by NSF Grant No. DMR-1308446.

Method for extracting lanthanides and actinides from acid solutions

DOEpatents

Horwitz, E. Philip; Kalina, Dale G.; Kaplan, Louis; Mason, George W.

1985-01-01

A process for the recovery of actinide and lanthanide values from aqueous acidic solutions with an organic extractant having the formula: ##STR1## where .phi. is phenyl, R.sup.1 is a straight or branched alkyl or alkoxyalkyl containing from 6 to 12 carbon atoms and R.sup.2 is an alkyl containing from 3 to 6 carbon atoms. The process is suitable for the separation of actinide and lanthanide values from fission product values found together in high level nuclear reprocessing waste solutions.

Gamma-irradiation of malic acid in aqueous solutions. [prebiotic significance

NASA Technical Reports Server (NTRS)

Negron-Mendoza, A.; Graff, R. L.; Ponnamperuma, C.

1980-01-01

The gamma-irradiation of malic acid in aqueous solutions was studied under initially oxygenated and oxygen-free conditions in an attempt to determine the possible interconversion of malic acid into other carboxylic acids, specifically those associated with Krebs cycle. The effect of dose on product formation of the system was investigated. Gas-liquid chromatography combined with mass spectrometry was used as the principal means of identification of the nonvolatile products. Thin layer chromatography and direct probe mass spectroscopy were also employed. The findings show that a variety of carboxylic acids are formed, with malonic and succinic acids in greatest abundance. These products have all been identified as being formed in the gamma-irradiation of acetic acid, suggesting a common intermediary. Since these molecules fit into a metabolic cycle, it is strongly suggestive that prebiotic pathways provided the basis for biological systems.

EPR studies of the vitamin K 1 semiquinone radical anion. Comparison to the electron acceptor A 1 in green plant photosystem I

NASA Astrophysics Data System (ADS)

Thurnauer, Marion C.; Brown, James W.; Gast, P.; Feezel, Laura L.

Suggestions that the electron acceptor, A 1, in Photosystem I is a quinone have come from both optical and epr experiments. Vitamin K 1 (phylloquinone) is present in the PSI complex with a stoichiometry of two molecules per reaction center. In order to determine if A 1 can be identified with vitamin K 1, X-band and Q-band epr properties of the vitamin K 1 radical anion in frozen alcohol solutions are examined. The results are compared to the epr properties that have been observed for the reduced A 1 acceptor in vivo. The g-values obtained for the vitamin K 1 radical anion are consistent with identifying A 1 with vitamin K 1.

Ginger extract as green corrosion inhibitor of mild steel in hydrochloric acid solution

NASA Astrophysics Data System (ADS)

Fidrusli, A.; Suryanto; Mahmood, M.

2018-01-01

Ginger extract as corrosion inhibitor from natural resources was studied to prevent corrosion of mild steel in acid media. Ginger rhizome was extracted to produce green corrosion inhibitor (G-1) while ginger powder bought at supermarket was also extract to form green corrosion inhibitor (G-2). Effectiveness of inhibitor in preventing corrosion process of mild steel was studied in 1.0 M of hydrochloric acid. The experiment of weight loss method and polarization technique were conducted to measure corrosion rate and inhibition efficiency of mild steel in solution containing 1.0 M of hydrochloric acid with various concentration of inhibitor at room temperature. The results showed that, the rate of corrosion dropped from 8.09 mmpy in solution containing no inhibitor to 0.72 mmpy in solution containing 150g/l inhibitor while inhibition efficiency up to 91% was obtained. The polarization curve in polarization experiments shows that the inhibition efficiency is 86% with high concentration of inhibitor. The adsorption of ginger extract on the surface of mild steel was observed by using optical microscope and the characterization analysis was done by using pH measurement method. When high concentration of green inhibitor in the acid solution is used, the pH at the surface of steel is increasing.

Electromembrane Surrounded Solid Phase Microextraction Followed by Injection Port Derivatization and Gas Chromatography-Flame Ionization Detector Analysis for Determination of Acidic Herbicides in Plant Tissue.

PubMed

Rezazadeh, Maryam; Yamini, Yadollah; Seidi, Shahram; Tahmasebi, Elham; Rezaei, Fatemeh

2014-04-09

Electromembrane surrounded solid phase microextraction (EM-SPME) of acidic herbicides was studied for the first time. In order to investigate the capability of this new microextraction technique to analyze acidic targets, chlorophenoxy acid (CPA) herbicides were quantified in plant tissue. 1-Octanol, was sustained in the pores of the wall of a hollow fiber and served as supported liquid membrane (SLM). Other EM-SPME related parameters, including extraction time, applied voltage, and pHs of the sample solution and the acceptor phase, were optimized using experimental design. A 20 min time frame was needed to reach the highest extraction efficiency of the analytes from a 24 mL alkaline sample solution across the organic liquid membrane and into the aqueous acceptor phase through a 50 V electrical field, and to their final adsorption on a carbonaceous anode. In addition to high sample cleanup, which made the proposed method appropriate for analysis of acidic compounds in a complicated media (plant tissue), 4.8% of 2-methyl-4-chlorophenoxyacetic acid (MCPA) and 0.6% of 2,4-dichlorophenoxyacetic acid (2,4-D) were adsorbed on the anode, resulting in suitable detection limits (less than 5 ng mL -1 ), and admissible repeatability and reproducibility (intra- and interassay precision were in the ranges of 5.2-8.5% and 8.8-12.0%, respectively). Linearity of the method was scrutinized within the ranges of 1.0-500.0 and 10.0-500.0 ng mL -1 for MCPA and 2,4-D, respectively, and coefficients of determination greater than 0.9958 were obtained. Optimal conditions of EM-SPME of the herbicides were employed for analysis of CPAs in whole wheat tissue.

Methanol Uptake By Low Temperature Aqueous Sulfuric Acid Solutions

NASA Technical Reports Server (NTRS)

Iraci, Laura T.; Essin, Andrew M.; Golden, David M.; Hipskind, R. Stephen (Technical Monitor)

2001-01-01

To evaluate the role of upper tropospheric and lower stratospheric aerosols in the global budget of methanol, the solubility and reactivity of CH3OH in aqueous sulfuric acid solutions are under investigation. Using standard uptake techniques in a Knudsen cell reactor, we have measured the effective Henry's law coefficient, H(*), for methanol dissolution into 45 to 70 percent by weight H2SO4. We find that methanol solubility ranges from 10(exp 5) to 10(exp 8) M/atm and increases with decreasing temperature and with increasing sulfuric acid content. These solubility measurements include uptake due to physical solvation and all rapid equilibria which are established in solution. Our data indicate that simple uptake by aqueous sulfuric acid particles will not be a significant sink for methanol in the UT/LS. These results differ from those recently reported in the literature, and an explanation of this disparity will be presented. In addition to solvation, reaction between primary alcohols and sulfuric acid does occur, leading to the production of alkyl sulfates. Literature values for the rate of this reaction suggest that formation of CH3OSO3H may proceed in the atmosphere but is not significant under our experimental conditions. Results obtained using a complementary equilibrium measurement technique confirm this directly. In addition, the extent of methanol sequestration via formation of mono- and dimethylsulfate will be evaluated under several atmospheric conditions.

Process for gasification using a synthetic CO.sub.2 acceptor

DOEpatents

Lancet, Michael S.; Curran, George P.

1980-01-01

A gasification process is disclosed using a synthetic CO.sub.2 acceptor consisting essentially of at least one compound selected from the group consisting of calcium oxide and calcium carbonate supported in a refractory carrier matrix, the carrier having the general formula Ca.sub.5 (SiO.sub.4).sub.2 CO.sub.3. A method for producing the synthetic CO.sub.2 acceptor is also disclosed.

Dye-Incorporated Polynaphthalenediimide Acceptor for Additive-Free High-Performance All-Polymer Solar Cells.

PubMed

Chen, Dong; Yao, Jia; Chen, Lie; Yin, Jingping; Lv, Ruizhi; Huang, Bin; Liu, Siqi; Zhang, Zhi-Guo; Yang, Chunhe; Chen, Yiwang; Li, Yongfang

2018-04-16

All-polymer solar cells (all-PSCs) can offer unique advantages for applications in flexible devices, and naphthalene diimide (NDI)-based polymer acceptors are the widely used polymer acceptors. However, their power conversion efficiency (PCE) still lags behind that of state-of-the-art polymer solar cells, due to low light absorption, suboptimal energy levels and the strong aggregation of the NDI-based polymer acceptor. Herein, a rhodanine-based dye molecule was introduced into the NDI-based polymer acceptor by simple random copolymerization and showed an improved light absorption coefficient, an up-shifted lowest unoccupied molecular orbital level and reduced crystallization. Consequently, additive-free all-PSCs demonstrated a high PCE of 8.13 %, which is one of the highest performance characteristics reported for all-PSCs to date. These results indicate that incorporating a dye into the n-type polymer gives insight into the precise design of high-performance polymer acceptors for all-PSCs. © 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Non-catalytic hydrogenation of VO2 in acid solution.

PubMed

Chen, Yuliang; Wang, Zhaowu; Chen, Shi; Ren, Hui; Wang, Liangxin; Zhang, Guobin; Lu, Yalin; Jiang, Jun; Zou, Chongwen; Luo, Yi

2018-02-26

Hydrogenation is an effective way to tune the property of metal oxides. It can conventionally be performed by doping hydrogen into solid materials with noble-metal catalysis, high-temperature/pressure annealing treatment, or high-energy proton implantation in vacuum condition. Acid solution naturally provides a rich proton source, but it should cause corrosion rather than hydrogenation to metal oxides. Here we report a facile approach to hydrogenate monoclinic vanadium dioxide (VO 2 ) in acid solution at ambient condition by placing a small piece of low workfunction metal (Al, Cu, Ag, Zn, or Fe) on VO 2 surface. It is found that the attachment of a tiny metal particle (~1.0 mm) can lead to the complete hydrogenation of an entire wafer-size VO 2 (>2 inch). Moreover, with the right choice of the metal a two-step insulator-metal-insulator phase modulation can even be achieved. An electron-proton co-doping mechanism has been proposed and verified by the first-principles calculations.

Toluene nitration in irradiated nitric acid and nitrite solutions

NASA Astrophysics Data System (ADS)

Elias, Gracy; Mincher, Bruce J.; Mezyk, Stephen P.; Muller, Jim; Martin, Leigh R.

2011-04-01

The kinetics, mechanisms, and stable products produced for the nitration of aryl alkyl mild ortho-para director toluene in irradiated nitric acid and neutral nitrite solutions were investigated using γ and pulse radiolysis. Electron pulse radiolysis was used to determine the bimolecular rate constants for the reaction of toluene with different transient species produced by irradiation. HPLC with UV detection, GC-MS and LC-MS, were used to assess the stable reaction products. Free-radical based nitration reaction products were found in irradiated acidic and neutral media. In 6.0 M HNO3, ring substitution, side chain substitution, and oxidation, produced different nitrated toluene products. For ring substitution, nitrogen oxide radicals were added mainly to cyclohexadienyl radicals, whereas for side chain substitution, these radicals were added to the carbon-centered benzyl radical produced by H-atom abstraction. In neutral nitrite solutions, radiolytically-induced ring nitration products approached a statistically random distribution, suggesting a direct free-radical reaction involving addition of the rad NO2 radical.

Two-step voltage dual electromembrane extraction: A new approach to simultaneous extraction of acidic and basic drugs.

PubMed

Asadi, Sakine; Nojavan, Saeed

2016-06-07

In the present work, acidic and basic drugs were simultaneously extracted by a novel method of high efficiency herein referred to as two-step voltage dual electromembrane extraction (TSV-DEME). Optimizing effective parameters such as composition of organic liquid membrane, pH values of donor and acceptor solutions, voltage and duration of each step, the method had its figures of merit investigated in pure water, human plasma, wastewater, and breast milk samples. Simultaneous extraction of acidic and basic drugs was done by applying potentials of 150 V and 400 V for 6 min and 19 min as the first and second steps, respectively. The model compounds were extracted from 4 mL of sample solution (pH = 6) into 20 μL of each acceptor solution (32 mM NaOH for acidic drugs and 32 mM HCL for basic drugs). 1-Octanol was immobilized within the pores of a porous hollow fiber of polypropylene, as the supported liquid membrane (SLM) for acidic drugs, and 2-ethyle hexanol, as the SLM for basic drugs. The proposed TSV-DEME technique provided good linearity with the resulting correlation coefficients ranging from 0.993 to 0.998 over a concentration range of 1-1000 ng mL(-1). The limit of detections of the drugs were found to range within 0.3-1.5 ng mL(-1), while the corresponding repeatability ranged from 7.7 to 15.5% (n = 4). The proposed method was further compared to simple dual electromembrane extraction (DEME), indicating significantly higher recoveries for TSV-DEME procedure (38.1-68%), as compared to those of simple DEME procedure (17.7-46%). Finally, the optimized TSV-DEME was applied to extract and quantify model compounds in breast milk, wastewater, and plasma samples. Copyright © 2016 Elsevier B.V. All rights reserved.

Corrosion property of 9Cr-ODS steel in nitric acid solution for spent nuclear fuel reprocessing

DOE Office of Scientific and Technical Information (OSTI.GOV)

Takeuchi, M.; Koizumi, T.; Inoue, M.

2013-07-01

Corrosion tests of oxide dispersion strengthened with 9% Cr (9Cr-ODS) steel, which is one of the desirable materials for cladding tube of sodium-cooled fast reactors, in pure nitric acid solution, spent FBR fuel solution, and its simulated solution were performed to understand the corrosion behavior in a spent nuclear fuel reprocessing. In this study, the 9Cr-ODS steel with lower effective chromium content was evaluated to understand the corrosion behavior conservatively. As results, the tube-type specimens of the 9Cr-ODS steels suffered severe weight loss owing to active dissolution at the beginning of the immersion test in pure nitric acid solution inmore » the range from 1 to 3.5 M. In contrast, the weight loss was decreased and they showed a stable corrosion in the higher nitric acid concentration, the dissolved FBR fuel solution, and its simulated solution by passivation. The corrosion rates of the 9Cr-ODS steel in the dissolved FBR fuel solution and its simulated solution were 1-2 mm/y and showed good agreement with each other. The passivation was caused by the shift of corrosion potential to noble side owing to increase in nitric acid concentration or oxidative ions in the dissolved FBR fuel solution and the simulated spent fuel solution. (authors)« less

Benzothiadiazole Versus Thiophene: Influence of the Auxiliary Acceptor on the Photovoltaic Properties of Donor-Acceptor-Based Copolymers.

PubMed

Li, Zongbo; Weng, Kangkang; Chen, Aihua; Sun, Xiaobo; Wei, Donghui; Yu, Mingming; Huo, Lijun; Sun, Yanming

2018-01-01

Two donor-acceptor (D-A) type conjugated copolymers, P1 and P2, are designed and synthesized. A classical benzothiadiazole acceptor is used to replace a thiophene unit in the polymer chain of P1 to obtain P2 terpolymer. Compared with P1, P2 exhibits broader absorption spectra, higher absorption coefficient, deeper lowest unoccupied molecular orbital level, and a relatively lower band gap. As a result, the P2-based solar cell exhibits a high power conversion efficiency (PCE) of 6.60%, with a short-circuit current (J sc ) of 12.43 mA cm -2 , and a fill factor (FF) of 73.1%, which are higher than those of the P1-based device with a PCE of 4.70%, a J sc of 9.43 mA cm -2 , and an FF of 61.6%. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

REDUCTION OF PLUTONIUM VALUES IN AN ACIDIC AQUEOUS SOLUTION WITH FORMALDEHYDE

DOEpatents

Olson, C.M.

1959-06-01

A method is given for reducing Pu to the tetravalent state and lowering the high acidity of dissolver solutions containing U and Pu. Formaldehyde is added to the HNO/sub 3/ solution of U and Pu to effect a formaldehyde to HNO/sub 3/ molar ratio of 0.375:1 to 1.5:1. The Pu can then be removed from the solution by carrier precipitation using BiPO/sub 4/ or by ion exchange. (T.R.H.)

High-Performance Organic Photodetectors from a High-Bandgap Indacenodithiophene-Based π-Conjugated Donor-Acceptor Polymer.

PubMed

Benavides, Cindy Montenegro; Murto, Petri; Chochos, Christos L; Gregoriou, Vasilis G; Avgeropoulos, Apostolos; Xu, Xiaofeng; Bini, Kim; Sharma, Anirudh; Andersson, Mats R; Schmidt, Oliver; Brabec, Christoph J; Wang, Ergang; Tedde, Sandro F

2018-04-18

A conjugated donor-acceptor polymer, poly[4,4,9,9-tetrakis(4-hexylphenyl)-4,9-dihydro- s-indaceno[1,2- b:5,6- b']dithiophene-2,7-diyl- alt-5-(2-ethylhexyl)-4 H-thieno[3,4- c]pyrrole-4,6(5 H)-dione-1,3-diyl] (PIDT-TPD), is blended with the fullerene derivative [6,6]phenyl-C61-butyric acid methyl ester (PC 61 BM) for the fabrication of thin and solution-processed organic photodetectors (OPDs). Systematic screening of the concentration ratio of the blend and the molecular weight of the polymer is performed to optimize the active layer morphology and the OPD performance. The device comprising a medium molecular weight polymer (27.0 kg/mol) in a PIDT-TPD:PC 61 BM 1:1 ratio exhibits an external quantum efficiency of 52% at 610 nm, a dark current density of 1 nA/cm 2 , a detectivity of 1.44 × 10 13 Jones, and a maximum 3 dB cutoff frequency of 100 kHz at -5 V bias. These results are remarkable among the state-of-the-art red photodetectors based on conjugated polymers. As such, this work presents a functional organic active material for high-speed OPDs with a linear photoresponse at different light intensities.

Aquatic photolysis: photolytic redox reactions between goethite and adsorbed organic acids in aqueous solutions

USGS Publications Warehouse

Goldberg, M.C.; Cunningham, K.M.; Weiner, Eugene R.

1993-01-01

Photolysis of mono and di-carboxylic acids that are adsorbed onto the surface of the iron oxyhydroxide (goethite) results in an oxidation of the organic material and a reduction from Fe(III) to Fe(II) in the iron complex. There is a subsequent release of Fe2+ ions into solution. At constant light flux and constant solution light absorption, the factors responsible for the degree of photolytic reaction include: the number of lattice sites that are bonded by the organic acid; the rate of acid readsorption to the surface during photolysis; the conformation and structure of the organic acid; the degree of oxidation of the organic acid; the presence or absence of an ??-hydroxy group on the acid, the number of carbons in the di-acid chain and the conformation of the di-acid. The ability to liberate Fe(III) at pH 6.5 from the geothite lattice is described by the lyotropic series: tartrate>citrate> oxalate > glycolate > maleate > succinate > formate > fumarate > malonate > glutarate > benzoate = butanoate = control. Although a larger amount of iron is liberated, the series is almost the same at pH 5.5 except that oxalate > citrate and succinate > maleate. A set of rate equations are given that describe the release of iron from the goethite lattice. It was observed that the pH of the solution increases during photolysis if the solutions are not buffered. There is evidence to suggest the primary mechanism for all these reactions is an electron transfer from the organic ligand to the Fe(III) in the complex. Of all the iron-oxyhydroxide materials, crystalline goethite is the least soluble in water; yet, this study indicates that in an aqueous suspension, iron can be liberated from the goethite lattice. Further, it has been shown that photolysis can occur in a multiphase system at the sediment- water interface which results in an oxidation of the organic species and release of Fe2+ to solution where it becomes available for further reaction. ?? 1993.

THE KINETICS OF SAPONIFICATION OF IODOACETIC ACID BY SODIUM HYDROXIDE AND BY CERTAIN ALKALINE BUFFER SOLUTIONS.

PubMed

Brdicka, R

1936-07-20

1. The rate of the saponification of iodoacetic acid in sodium hydroxide and alkaline buffer solutions yielding glycollic acid was measured by means of Heyrovský's polarographic method. 2. From the bimolecular velocity constants, increasing with the ionic strength of the solution, the Brönsted factor, F, which characterizes the primary salt effect, was calculated. 3. In the borate buffer solutions the monomolecular constants of the saponification were determined which, at values above the pH of neutralization of boric acid, show a proportionality to the concentration of hydroxyl anions. Below the pH of neutralization of boric acid, they are proportional to the concentration of borate anions.

Targeting ideal acceptor-donor materials based on hexabenzocoronene

NASA Astrophysics Data System (ADS)

Santos Silva, H.; Metz, Sebastian; Hiorns, Roger C.; Bégué, D.

2018-06-01

A series of new hybrid donor-acceptor materials based on hexabenzocoronenes (HBC) functionalized with electron donors is investigated by combining a variety of quantum mechanical and molecular dynamic methodologies for use in organic photovoltaic (OPV) devices. Segments of a low band gap alternating copolymer constructed of benzo[1,2-b;3,4-b]dithiophene and thieno[3,4-c]pyrrole-4,6-dione were attached to the conjugated HBC core. The copolymer was chosen for its known high performance in OPVs, and both moieties were singled out due to their exceptional resistance to photo-oxidation, an important requirement for such applications. The macromolecular topology of these systems are expected to induce supra-molecular columns, such as those common to discotic liquid crystals, conducive to the effective percolation of electrons in OPV devices. A challenge with these systems, that of the mixing of the electronic structures of the donor and acceptor moieties that result in excitonic losses and charge recombination, was diminished by trialling a range of linking units. It was found possible to propose ideal donor-acceptor structures with enhanced charge dissociations and transfers in the π-stacking direction for use in OPV and other organic electronic devices.

Fine-tuning of electronic properties in donor-acceptor conjugated polymers based on oligothiophenes

NASA Astrophysics Data System (ADS)

Imae, Ichiro; Sagawa, Hitoshi; Harima, Yutaka

2018-03-01

A novel series of donor-acceptor conjugated polymers having oligothiophenes with well-defined structures were synthesized and their optical, electrochemical, and photovoltaic properties were investigated. It was found that the absorption bands of polymers were red-shifted with increasing number of ethylenedioxy groups added to each oligothiophene unit and that their band edges reached over 1000 nm. The systematical fine-tuning of the electronic properties was achieved using the chemical structures of oligothiophene units. Photovoltaic cells based on polymer/(6,6)-phenyl C61 butyric acid methyl ester (PC61BM) exhibited power conversion efficiencies in the range from 0.004 to 1.10%, reflecting the electronic properties of the polymers.

Electron acceptor redox potential globally regulates transcriptomic profiling in Shewanella decolorationis S12

NASA Astrophysics Data System (ADS)

Lian, Yingli; Yang, Yonggang; Guo, Jun; Wang, Yan; Li, Xiaojing; Fang, Yun; Gan, Lixia; Xu, Meiying

2016-08-01

Electron acceptor redox potential (EARP) was presumed to be a determining factor for microbial metabolism in many natural and engineered processes. However, little is known about the potentially global effects of EARP on bacteria. In this study, we compared the physiological and transcriptomic properties of Shewanella decolorationis S12 respiring with different EARPs in microbial electrochemical systems to avoid the effects caused by the other physicochemical properties of real electron acceptor. Results showed that the metabolic activities of strain S12 were nonlinear responses to EARP. The tricarboxylic acid cycle for central carbon metabolism was down-regulated while glyoxylate shunt was up-regulated at 0.8 V compared to 0.2 and -0.2 V, which suggested that EARP is an important but not the only determinant for metabolic pathways of strain S12. Moreover, few cytochrome c genes were differentially expressed at different EARPs. The energy intensive flagella assembly and assimilatory sulfur metabolism pathways were significantly enriched at 0.8 V, which suggested strain S12 had stronger electrokinesis behavior and oxidative stress-response at high EARP. This study provides the first global information of EARP regulations on microbial metabolism, which will be helpful for understanding microorganism respiration.

Quenching characteristics of bathocuproinedisulfonic acid, disodium salt in aqueous solution and copper sulfate plating solution

NASA Astrophysics Data System (ADS)

Koga, Toshiaki; Hirakawa, Chieko; Takeshita, Michinori; Terasaki, Nao

2018-04-01

Bathocuproinedisulfonic acid, disodium salt (BCS) is generally used to detect Cu(I) through a color reaction. We newly found BCS fluorescence in the visible blue region in an aqueous solution. However, the fluorescence mechanism of BCS is not well known, so we should investigate its fundamental information. We confirmed that the characteristics of fluorescence are highly dependent on the molecular concentration and solvent properties. In particular, owing to the presence of the copper compound, the fluorescence intensity extremely decreases. By fluorescence quenching, we observed that a copper compound concentration of 10-6 mol/L or less could easily be measured in an aqueous solution. We also observed BCS fluorescence in copper sulfate plating solution and the possibility of detecting monovalent copper by fluorescence reabsorption.

Three phases hollow fiber LPME combined with HPLC-UV for extraction, preconcentration and determination of valerenic acid in Valeriana officinalis.

PubMed

Mirzaei, Mohamad; Dinpanah, Hossein

2011-07-01

In the present work, the applicability of hollow fiber-based liquid phase microextraction (HF-LPME) was evaluated for the extraction and preconcentration of valerenic acid prior to its determination by reversed-phase HPLC/UV. The target drug was extracted from 5.0 mL of aqueous solution with pH 3.5 into an organic extracting solvent (dihexyl ether) impregnated in the pores of a hollow fiber and finally back extracted into 10 μ L of aqueous solution with pH 9.5 located inside the lumen of the hollow fiber. In order to obtain high extraction efficiency, the parameters affecting the HF-LPME, including pH of the donor and acceptor phases, type of organic phase, ionic strength, the volume ratio of donor to acceptor phase, stirring rate and extraction time were studied and optimized. Under the optimized conditions, enrichment factor up to 446 was achieved and the relative standard deviation (RSD) of the method was 4.36% (n = 9). The linear range was 7.5-850 μg L⁻¹ with correlation coefficient (r²=0.999), detection limits was 2.5 μg L⁻¹ and the LOQ was 7.5 μg L⁻¹. The proposed method was evaluated by extraction and determination of valerenic acid in some Iranian wild species of Valerianaceae. Copyright © 2011 Elsevier B.V. All rights reserved.

Time dependent inhibition of xanthine oxidase in irradiated solutions of folic acid, aminopterin and methotrexate

DOE Office of Scientific and Technical Information (OSTI.GOV)

Robinson, K.; Pilot, T.F.; Meany, J.E.

1990-01-01

The xanthine oxidase catalyzed oxidation of hypoxanthine was followed by monitoring the formation of uric acid at 290 nm. Inhibition of xanthine oxidase occurs in aqueous solutions of folic acid methotrexate and aminopterin. These compounds are known to dissociate upon exposure to ultraviolet light resulting in the formation of their respective 6-formylpteridine derivatives. The relative rates of dissociation were monitored spectrophotometrically by determining the absorbance of their 2,4-dinitrophenylhydrazine derivatives at 500 nm. When aqueous solutions of folic acid, aminopterin and methotrexate were exposed to uv light, a direct correlation was observed between the concentrations of the 6-formylpteridine derivatives existing inmore » solution and the ability of these solutions to inhibit xanthine oxidase. The relative potency of the respective photolysis products were estimated.« less

Solvent Properties of Water in Aqueous Solutions of Elastin-Like Polypeptide

PubMed Central

Ferreira, Luisa A.; Cole, James T.; Reichardt, Christian; Holland, Nolan B.; Uversky, Vladimir N.; Zaslavsky, Boris Y.

2015-01-01

The phase-transition temperatures of an elastin-like polypeptide (ELP) with the (GVGVP)40 sequence and solvent dipolarity/polarizability, hydrogen-bond donor acidity, and hydrogen-bond acceptor basicity in its aqueous solutions were quantified in the absence and presence of different salts (Na2SO4, NaCl, NaClO4, and NaSCN) and various osmolytes (sucrose, sorbitol, trehalose, and trimethylamine N-oxide (TMAO)). All osmolytes decreased the ELP phase-transition temperature, whereas NaCl and Na2SO4 decreased, and NaSCN and NaClO4 increased it. The determined phase-transition temperatures may be described as a linear combination of the solvent’s dipolarity/polarizability and hydrogen-bond donor acidity. The linear relationship established for the phase-transition temperature in the presence of salts differs quantitatively from that in the presence of osmolytes, in agreement with different (direct and indirect) mechanisms of the influence of salts and osmolytes on the ELP phase-transition temperature. PMID:26075870

Nitrogen Oxides in Early Earth's Atmosphere as Electron Acceptors for Life's Emergence

NASA Astrophysics Data System (ADS)

Wong, Michael L.; Charnay, Benjamin D.; Gao, Peter; Yung, Yuk L.; Russell, Michael J.

2017-10-01

We quantify the amount of nitrogen oxides (NOx) produced through lightning and photochemical processes in the Hadean atmosphere to be available in the Hadean ocean for the emergence of life. Atmospherically generated nitrate (NO3-) and nitrite (NO2-) are the most attractive high-potential electron acceptors for pulling and enabling crucial redox reactions of autotrophic metabolic pathways at submarine alkaline hydrothermal vents. The Hadean atmosphere, dominated by CO2 and N2, will produce nitric oxide (NO) when shocked by lightning. Photochemical reactions involving NO and H2O vapor will then produce acids such as HNO, HNO2, HNO3, and HO2NO2 that rain into the ocean. There, they dissociate into or react to form nitrate and nitrite. We present new calculations based on a novel combination of early-Earth global climate model and photochemical modeling, and we predict the flux of NOx to the Hadean ocean. In our 0.1-, 1-, and 10-bar pCO2 models, we calculate the NOx delivery to be 2.4 × 105, 6.5 × 108, and 1.9 × 108 molecules cm-2 s-1. After only tens of thousands to tens of millions of years, these NOx fluxes are expected to produce sufficient (micromolar) ocean concentrations of high-potential electron acceptors for the emergence of life.

Synthesis and characterization of donor-acceptor copolymers carrying triphenylamine units for photovoltaic applications

NASA Astrophysics Data System (ADS)

Neumann, Katharina; Thelakkat, Mukundan

2012-09-01

The synthesis and analysis of solution processable polymers for organic solar cells is crucial for innovative solar cell technologies such as printing processes. In the field of donor materials for photovoltaic applications, polymers based on tetraphenylamine (TPA) are well known hole conducting materials. Here, we synthesized two conjugated TPA containing copolymers via Suzuki polycondensation. We investigated the tuning of the energy levels of the TPA based polymers by two different concepts. Firstly, we introduced an acceptor unit in the side chain. The main-chain of this copolymer was built from TPA units. The resulting copolymer 2-(4-((4'-((4-(2-ethylhexyloxy)phenyl)(paratolyl) amino)biphenyl-4-yl)(para-tolyl)amino)benzylidene) malononitrile P1 showed a broader absorption up to 550 nm. Secondly, we used a donor-acceptor concept by synthesizing a copolymer with alternating electron donating TPA and electron withdrawing Thieno[3,4-b]thiophene ester units. Consequently, the absorption maximum in the copolymer octyl-6-(4-((4-(2-ethylhexyloxy)phenyl)(p-tolyl)amino)phenyl)-4-methylthieno[3,4-b]thiophene-2-carboxylate P2 was red shifted to 580 nm. All three polymers showed high thermal stability. By UV-vis and Cyclic voltammetry measurements the optical and electrochemical properties of the polymers were analyzed.

Direct sensing of fluoride in aqueous solutions using a boronic acid based sensor.

PubMed

Wu, Xin; Chen, Xuan-Xuan; Song, Bing-Nan; Huang, Yan-Jun; Ouyang, Wen-Juan; Li, Zhao; James, Tony D; Jiang, Yun-Bao

2014-11-21

Binding of the fluoride ion triggers aggregation of a pyreneboronic acid-catechol ensemble in acidic aqueous solutions, giving rise to intense excimer emission, allowing for sensitive fluoride ion sensing at ppm levels, with an apparent fluoride binding constant higher than 10(3) M(-1) which is unprecedented for boronic acid sensors in water.

Tetrahydrothiophene 1-oxide as an electron acceptor for Escherichia coli.

PubMed Central

Meganathan, R; Schrementi, J

1987-01-01

Escherichia coli used tetrahydrothiophene 1-oxide (THTO) as an electron acceptor for anaerobic growth with glycerol as a carbon source; the THTO was reduced to tetrahydrothiophene. Cell extracts also reduced THTO to tetrahydrothiophene in the presence of a variety of electron donors. Chlorate-resistant (chl) mutants (chlA, chlB, chlD, and chlE) were unable to grow with THTO as the electron acceptor. However, growth and THTO reduction by the chlD mutant were restored by high concentrations of molybdate. Similarly, mutants of E. coli that are blocked in the menaquinone (vitamin K2) biosynthetic pathway, i.e., menB, menC, and menD mutants, did not grow with THTO as an electron acceptor. Growth and THTO reduction were restored in these mutants by the presence of appropriate intermediates of the vitamin K biosynthetic pathway. PMID:3294808

THE KINETICS OF SAPONIFICATION OF IODOACETIC ACID BY SODIUM HYDROXIDE AND BY CERTAIN ALKALINE BUFFER SOLUTIONS

PubMed Central

Brdička, R.

1936-01-01

1. The rate of the saponification of iodoacetic acid in sodium hydroxide and alkaline buffer solutions yielding glycollic acid was measured by means of Heyrovský's polarographic method. 2. From the bimolecular velocity constants, increasing with the ionic strength of the solution, the Brönsted factor, F, which characterizes the primary salt effect, was calculated. 3. In the borate buffer solutions the monomolecular constants of the saponification were determined which, at values above the pH of neutralization of boric acid, show a proportionality to the concentration of hydroxyl anions. Below the pH of neutralization of boric acid, they are proportional to the concentration of borate anions. PMID:19872968

Degradation of hydroxycinnamic acid mixtures in aqueous sucrose solutions by the Fenton process.

PubMed

Nguyen, Danny M T; Zhang, Zhanying; Doherty, William O S

2015-02-11

The degradation efficiencies and behaviors of caffeic acid (CaA), p-coumaric acid (pCoA), and ferulic acid (FeA) in aqueous sucrose solutions containing the mixture of these hydroxycinnamic acids (HCAs) were studied by the Fenton oxidation process. Central composite design and multiresponse surface methodology were used to evaluate and optimize the interactive effects of process parameters. Four quadratic polynomial models were developed for the degradation of each individual acid in the mixture and the total HCAs degraded. Sucrose was the most influential parameter that significantly affected the total amount of HCA degraded. Under the conditions studied there was a <0.01% loss of sucrose in all reactions. The optimal values of the process parameters for a 200 mg/L HCA mixture in water (pH 4.73, 25.15 °C) and sucrose solution (13 mass %, pH 5.39, 35.98 °C) were 77% and 57%, respectively. Regression analysis showed goodness of fit between the experimental results and the predicted values. The degradation behavior of CaA differed from those of pCoA and FeA, where further CaA degradation is observed at increasing sucrose and decreasing solution pH. The differences (established using UV/vis and ATR-FTIR spectroscopy) were because, unlike the other acids, CaA formed a complex with Fe(III) or with Fe(III) hydrogen-bonded to sucrose and coprecipitated with lepidocrocite, an iron oxyhydroxide.

Changes in properties of polyacid-modified composite resins (compomers) following storage in acidic solutions.

PubMed

Nicholson, J W; Gjorgievska, E; Bajraktarova, B; McKenzie, M A

2003-06-01

The interaction of three polyacid-modified composite resins (compomers) with various acidic storage solutions, and also water, over periods of time up to 6 months has been studied and compared with those of a glass-ionomer and a composite resin. This interaction has been shown to vary in a complex way with length of storage and nature of the acid, and citric acid was found to be the most aggressive storage medium for glass-ionomer cement, and also for the compomers. The pure composite resin, by contrast, was relatively unaffected by all of the acid solutions examined. In all acids, the compomers showed a distinct buffering effect, i.e. they increased the pH towards neutral, as did the glass-ionomer. The extent of this also varied with duration of storage and nature of the acid. The biaxial flexure strength was determined and found to be essentially unaffected by the complex chemical interactions with acidic storage solutions. Values obtained for the compomers were lower than those of the composite resin, but above those of the glass-ionomer. Fourier-transform infrared (FT-IR) spectroscopy was employed to study the changes in the compomers following storage in the aqueous media, but bands were broad and no detailed assignments could be made. There were changes in the region of the spectra associated with metal carboxylates however, and this indicates that the secondary acid-base reaction had occurred following water uptake.

The thermochemical characteristics of solution of phenol and benzoic acid in water-dimethylsulfoxide and water-acetonitrile mixtures

NASA Astrophysics Data System (ADS)

Zakharov, A. G.; Voronova, M. I.; Batov, D. V.; Smirnova, K. V.

2011-03-01

The solution of phenol and benzoic acid in water-dimethylsulfoxide (DMSO) and water-acetonitrile (AN) mixtures was studied. As distinct from benzoic acid, the thermodynamic characteristics of solution of phenol sharply change at concentrations corresponding to a change in the character of cluster formation in water-DMSO and water-AN mixtures. Differences in the solvation of phenol and benzoic acid are explained by different mechanisms of the interaction of the solutes with clusters existing in binary mixtures.

Formation of amino acids by cobalt-60 irradiation of hydrogen cyanide solutions

NASA Technical Reports Server (NTRS)

Sweeney, M. A.; Toste, A. P.; Ponnamperuma, C.

1976-01-01

Experiments were conducted to study the pathway for the prebiotic origin of amino acids from hydrogen cyanide (HCN) under the action of ionizing radiation considered as an effective source of energy on the primitive earth. The irradiations were performed in a cobalt-60 source with a dose rate of 200,000 rad/hr. Seven naturally occurring amino acids are identified among the products formed by the hydrolysis of gamma-irradiated solutions of HCN: glycine, alanine, valine, serine, threonine, aspartic acid, and glutamic acid. The identity of these amino acids is established by gas chromatography and mass spectrometry. Control experiments provided evidence that the amino acids are not the result of contamination.

Study of stability of methotrexate in acidic solution spectrofluorimetric determination of methotrexate in pharmaceutical preparations through acid-catalyzed degradation reaction.

PubMed

Sabry, Suzy M; Abdel-Hady, M; Elsayed, M; Fahmy, Osama T; Maher, Hadir M

2003-07-14

Study of the degradation reaction of methotrexate (MTX) in acidic solution was carried out. Optimization of the experimental parameters of MTX acid hydrolysis was investigated. Spectrofluorimetric method for determination of MTX through measurement of its acid-degradation product, 4-amino-4-deoxy-10-methylpteroic acid (AMP), was developed. Stability of the standard solution of MTX prepared in sulfuric acid was discussed in the view of accelerated stability analysis. Two other comparative spectroflourimetric methods based on measuring the fluorescence intensities from either a condensation reaction with acetylacetone-formaldehyde (Hantzsch reaction) or a reaction with fluorescamine were also described. Beer's law validation, accuracy, precision, limits of detection, limits of quantification, and other aspects of analytical merit are presented in the text. The proposed methods were successfully applied for the analysis of MTX in pure drug and tablets dosage form. The sensitivity of the developed methods was favorable, so it was possible to be adopted for determination of MTX in plasma samples for routine use in high-dose MTX therapy.

Electron-Transfer Dynamics for a Donor-Bridge-Acceptor Complex in Ionic Liquids.

PubMed

DeVine, Jessalyn A; Labib, Marena; Harries, Megan E; Rached, Rouba Abdel Malak; Issa, Joseph; Wishart, James F; Castner, Edward W

2015-08-27

Intramolecular photoinduced electron transfer from an N,N-dimethyl-p-phenylenediamine donor bridged by a diproline spacer to a coumarin 343 acceptor was studied using time-resolved fluorescence measurements in three ionic liquids and in acetonitrile. The three ionic liquids have the bis[(trifluoromethyl)sulfonyl]amide anion paired with the tributylmethylammonium, 1-butyl-1-methylpyrrolidinium, and 1-decyl-1-methylpyrrolidinium cations. The dynamics in the two-proline donor-bridge-acceptor complex are compared to those observed for the same donor and acceptor connected by a single proline bridge, studied previously by Lee et al. (J. Phys. Chem. C 2012, 116, 5197). The increased conformational freedom afforded by the second bridging proline resulted in multiple energetically accessible conformations. The multiple conformations have significant variations in donor-acceptor electronic coupling, leading to dynamics that include both adiabatic and nonadiabatic contributions. In common with the single-proline bridged complex, the intramolecular electron transfer in the two-proline system was found to be in the Marcus inverted regime.

Evolution of rosmarinic acid biosynthesis.

PubMed

Petersen, Maike; Abdullah, Yana; Benner, Johannes; Eberle, David; Gehlen, Katja; Hücherig, Stephanie; Janiak, Verena; Kim, Kyung Hee; Sander, Marion; Weitzel, Corinna; Wolters, Stefan

2009-01-01

Rosmarinic acid and chlorogenic acid are caffeic acid esters widely found in the plant kingdom and presumably accumulated as defense compounds. In a survey, more than 240 plant species have been screened for the presence of rosmarinic and chlorogenic acids. Several rosmarinic acid-containing species have been detected. The rosmarinic acid accumulation in species of the Marantaceae has not been known before. Rosmarinic acid is found in hornworts, in the fern family Blechnaceae and in species of several orders of mono- and dicotyledonous angiosperms. The biosyntheses of caffeoylshikimate, chlorogenic acid and rosmarinic acid use 4-coumaroyl-CoA from the general phenylpropanoid pathway as hydroxycinnamoyl donor. The hydroxycinnamoyl acceptor substrate comes from the shikimate pathway: shikimic acid, quinic acid and hydroxyphenyllactic acid derived from l-tyrosine. Similar steps are involved in the biosyntheses of rosmarinic, chlorogenic and caffeoylshikimic acids: the transfer of the 4-coumaroyl moiety to an acceptor molecule by a hydroxycinnamoyltransferase from the BAHD acyltransferase family and the meta-hydroxylation of the 4-coumaroyl moiety in the ester by a cytochrome P450 monooxygenase from the CYP98A family. The hydroxycinnamoyltransferases as well as the meta-hydroxylases show high sequence similarities and thus seem to be closely related. The hydroxycinnamoyltransferase and CYP98A14 from Coleus blumei (Lamiaceae) are nevertheless specific for substrates involved in RA biosynthesis showing an evolutionary diversification in phenolic ester metabolism. Our current view is that only a few enzymes had to be "invented" for rosmarinic acid biosynthesis probably on the basis of genes needed for the formation of chlorogenic and caffeoylshikimic acid while further biosynthetic steps might have been recruited from phenylpropanoid metabolism, tocopherol/plastoquinone biosynthesis and photorespiration.

Method for extracting lanthanides and actinides from acid solutions by modification of Purex solvent

DOEpatents

Horwitz, E.P.; Kalina, D.G.

1984-05-21

A process has been developed for the extraction of multivalent lanthanide and actinide values from acidic waste solutions, and for the separation of these values from fission product and other values, which utilizes a new series of neutral bi-functional extractants, the alkyl(phenyl)-N, N-dialkylcarbamoylmethylphosphine oxides, in combination with a phase modifier to form an extraction solution. The addition of the extractant to the Purex process extractant, tri-n-butylphosphate in normal paraffin hydrocarbon diluent, will permit the extraction of multivalent lanthanide and actinide values from 0.1 to 12.0 molar acid solutions.

High-efficiency and air-stable P3HT-based polymer solar cells with a new non-fullerene acceptor

PubMed Central

Holliday, Sarah; Ashraf, Raja Shahid; Wadsworth, Andrew; Baran, Derya; Yousaf, Syeda Amber; Nielsen, Christian B.; Tan, Ching-Hong; Dimitrov, Stoichko D.; Shang, Zhengrong; Gasparini, Nicola; Alamoudi, Maha; Laquai, Frédéric; Brabec, Christoph J.; Salleo, Alberto; Durrant, James R.; McCulloch, Iain

2016-01-01

Solution-processed organic photovoltaics (OPV) offer the attractive prospect of low-cost, light-weight and environmentally benign solar energy production. The highest efficiency OPV at present use low-bandgap donor polymers, many of which suffer from problems with stability and synthetic scalability. They also rely on fullerene-based acceptors, which themselves have issues with cost, stability and limited spectral absorption. Here we present a new non-fullerene acceptor that has been specifically designed to give improved performance alongside the wide bandgap donor poly(3-hexylthiophene), a polymer with significantly better prospects for commercial OPV due to its relative scalability and stability. Thanks to the well-matched optoelectronic and morphological properties of these materials, efficiencies of 6.4% are achieved which is the highest reported for fullerene-free P3HT devices. In addition, dramatically improved air stability is demonstrated relative to other high-efficiency OPV, showing the excellent potential of this new material combination for future technological applications. PMID:27279376

Radiation-induced degradation of cyclohexanebutyric acid in aqueous solutions by gamma ray irradiation

NASA Astrophysics Data System (ADS)

Jia, Wenbao; He, Yanquan; Ling, Yongsheng; Hei, Daqian; Shan, Qing; Zhang, Yan; Li, Jiatong

2015-04-01

The radiation-induced degradation of cyclohexanebutyric acid under gamma ray irradiation was investigated. Degradation experiments were performed with 100 mL sealed Pyrex glass vessels loaded with 80 mL of cyclohexanebutyric acid solutions at various initial concentrations of 10, 20, and 40 mg L-1. The absorbed doses were controlled at 0, 0.65, 1.95, 3.25, 6.5, 9.75, and 13 kGy. The results showed that gamma ray irradiation could effectively degrade cyclohexanebutyric acid in aqueous solutions. The removal rate of cyclohexanebutyric acid increased significantly with the increase of absorbed dose and the decrease of its initial concentration. At the same time, the removal of chemical oxygen demand (COD) was as effective as that of cyclohexanebutyric acid. The kinetic studies showed that the degradation of cyclohexanebutyric acid followed pseudo first-order reaction. Above all, the proposed mechanism obtained when NaNO2, NaNO3 and tert-butanol were added showed that the •OH radical played a major role in the gamma degradation process of cyclohexanebutyric acid, while •H and eaq- played a minor role in the gamma degradation process. The degradation products were identified by Fourier transform infrared spectroscopy (FTIR) and gas chromatography/mass spectrometry (GC/MS) during cyclohexanebutyric acid degradation.

Utilization of charge-transfer complexation for the detection of carcinogenic substances in foods: Spectroscopic characterization of ethyl carbamate with some traditional π-acceptors

NASA Astrophysics Data System (ADS)

Adam, Abdel Majid A.; Refat, Moamen S.; Saad, Hosam A.

2013-04-01

The study of toxic and carcinogenic substances in foods represents one of the most demanding areas in food safety, due to their repercussions for public health. One potentially toxic compound for humans is ethyl carbamate (EC). EC is a multi-site genotoxic carcinogen of widespread occurrence in fermented foods and alcoholic beverages. Structural and thermal stability of charge-transfer complexes formed between EC as a donor with quinol (QL), picric acid (PA), chloranilic acid (CLA), p-chloranil (p-CHL) and 1,3-dinitrobenzene (DNB) as acceptors were reported. Elemental analysis (CHN), electronic absorption spectra, photometric titration, IR, and 1H NMR spectra show that the interaction between EC and acceptors was stabilized by hydrogen bonding, via a 1:1 stoichiometry. Thermogravimetric (TG) analysis indicates that the formation of molecular CT complexes was stable, exothermic and spontaneous. Finally, the CT complexes were screened for their antibacterial and antifungal activities. The results indicated that the [(EC)(QL)] complex exhibited strong antimicrobial activities against various bacterial and fungal strains compared with standard drugs.

New Splice Site Acceptor Mutation in AIRE Gene in Autoimmune Polyendocrine Syndrome Type 1

PubMed Central

Mora, Mireia; Hanzu, Felicia A.; Pradas-Juni, Marta; Aranda, Gloria B.; Halperin, Irene; Puig-Domingo, Manuel; Aguiló, Sira; Fernández-Rebollo, Eduardo

2014-01-01

Autoimmune polyglandular syndrome type 1 (APS-1, OMIM 240300) is a rare autosomal recessive disorder, characterized by the presence of at least two of three major diseases: hypoparathyroidism, Addison’s disease, and chronic mucocutaneous candidiasis. We aim to identify the molecular defects and investigate the clinical and mutational characteristics in an index case and other members of a consanguineous family. We identified a novel homozygous mutation in the splice site acceptor (SSA) of intron 5 (c.653-1G>A) in two siblings with different clinical outcomes of APS-1. Coding DNA sequencing revealed that this AIRE mutation potentially compromised the recognition of the constitutive SSA of intron 5, splicing upstream onto a nearby cryptic SSA in intron 5. Surprisingly, the use of an alternative SSA entails the uncovering of a cryptic donor splice site in exon 5. This new transcript generates a truncated protein (p.A214fs67X) containing the first 213 amino acids and followed by 68 aberrant amino acids. The mutation affects the proper splicing, not only at the acceptor but also at the donor splice site, highlighting the complexity of recognizing suitable splicing sites and the importance of sequencing the intron-exon junctions for a more precise molecular diagnosis and correct genetic counseling. As both siblings were carrying the same mutation but exhibited a different APS-1 onset, and one of the brothers was not clinically diagnosed, our finding highlights the possibility to suspect mutations in the AIRE gene in cases of childhood chronic candidiasis and/or hypoparathyroidism otherwise unexplained, especially when the phenotype is associated with other autoimmune diseases. PMID:24988226

Stability of antimicrobial activity of peracetic acid solutions used in the final disinfection process.

PubMed

Costa, Solange Alves da Silva; Paula, Olívia Ferreira Pereira de; Silva, Célia Regina Gonçalves E; Leão, Mariella Vieira Pereira; Santos, Silvana Soléo Ferreira dos

2015-01-01

The instruments and materials used in health establishments are frequently exposed to microorganism contamination, and chemical products are used before sterilization to reduce occupational infection. We evaluated the antimicrobial effectiveness, physical stability, and corrosiveness of two commercial formulations of peracetic acid on experimentally contaminated specimens. Stainless steel specimens were contaminated with Staphylococcus aureus, Escherichia coli, Candida albicans, blood, and saliva and then immersed in a ready peracetic acid solution: 2% Sekusept Aktiv (SA) or 0.25% Proxitane Alpha (PA), for different times. Then, washes of these instruments were plated in culture medium and colony-forming units counted. This procedure was repeated six times per day over 24 non-consecutive days. The corrosion capacity was assessed with the mass loss test, and the concentration of peracetic acid and pH of the solutions were measured with indicator tapes. Both SA and PA significantly eliminated microorganisms; however, the SA solution was stable for only 4 days, whereas PA remained stable throughout the experiment. The concentration of peracetic acid in the SA solutions decreased over time until the chemical was undetectable, although the pH remained at 5. The PA solution had a concentration of 500-400 mg/L and a pH of 2-3. Neither formulation induced corrosion and both reduced the number of microorganisms (p = 0.0001). However, the differences observed in the performance of each product highlight the necessity of establishing a protocol for optimizing the use of each one.

A 25% tannic acid solution as a root canal irrigant cleanser: a scanning electron microscope study.

PubMed

Bitter, N C

1989-03-01

A scanning electron microscope was used to evaluate the cleansing properties of a 25% tannic acid solution on the dentinal surface in the pulp chamber of endodontically prepared teeth. This was compared with the amorphous smear layer of the canal with the use of hydrogen peroxide and sodium hypochlorite solution as an irrigant. The tannic acid solution removed the smear layer more effectively than the regular cleansing agent.

Highly Soluble Benzo[ghi]perylenetriimide Derivatives: Stable and Air-Insensitive Electron Acceptors for Artificial Photosynthesis.

PubMed

Chen, Hung-Cheng; Hsu, Chao-Ping; Reek, Joost N H; Williams, René M; Brouwer, Albert M

2015-11-01

A series of new benzo[ghi]perylenetriimide (BPTI) derivatives has been synthesized and characterized. These remarkably soluble BPTI derivatives show strong optical absorption in the range of λ=300-500 nm and have a high triplet-state energy of 1.67 eV. A cyanophenyl substituent renders BPTI such a strong electron acceptor (Ered =-0.11 V vs. the normal hydrogen electrode) that electron-trapping reactions with O2 and H2 O do not occur. The BPTI radical anion on a fluorine-doped tin oxide|TiO2 electrode is persistent up to tens of seconds (t1/2 =39 s) in air-saturated buffer solution. As a result of favorable packing, theoretical electron mobilities (10(-2) ∼10(-1) cm(2) V(-1) s(-1)) are high and similar to the experimental values observed for perylene diimide and C60 derivatives. Our studies show the potential of the cyanophenyl-modified BPTI compounds as electron acceptors in devices for artificial photosynthesis in water splitting that are also very promising nonfullerene electron-transport materials for organic solar cells. © 2015 The Authors. Published by Wiley-VCH Verlag GmbH & Co. KGaA.

Exploring the formation pathways of donor-acceptor catenanes in aqueous dynamic combinatorial libraries.

PubMed

Cougnon, Fabien B L; Au-Yeung, Ho Yu; Pantoş, G Dan; Sanders, Jeremy K M

2011-03-09

The discovery through dynamic combinatorial chemistry (DCC) of a new generation of donor-acceptor [2]catenanes highlights the power of DCC to access unprecedented structures. While conventional thinking has limited the scope of donor-acceptor catenanes to strictly alternating stacks of donor (D) and acceptor (A) aromatic units, DCC is demonstrated in this paper to give access to unusual DAAD, DADD, and ADAA stacks. Each of these catenanes has specific structural requirements, allowing control of their formation. On the basis of these results, and on the observation that the catenanes represent kinetic bottlenecks in the reaction pathway, we propose a mechanism that explains and predicts the structures formed. Furthermore, the spontaneous assembly of catenanes in aqueous dynamic systems gives a fundamental insight into the role played by hydrophobic effect and donor-acceptor interactions when building such complex architectures.

Determination of acid ionization constants for weak acids by osmometry and the instrumental analysis self-evaluation feedback approach to student preparation of solutions

NASA Astrophysics Data System (ADS)

Kakolesha, Nyanguila

One focus of this work was to develop of an alternative method to conductivity for determining the acid ionization constants. Computer-controlled osmometry is one of the emerging analytical tools in industrial research and clinical laboratories. It is slowly finding its way into chemistry laboratories. The instrument's microprocessor control ensures shortened data collection time, repeatability, accuracy, and automatic calibration. The equilibrium constants of acetic acid, chloroacetic acid, bromoacetic acid, cyanoacetic acid, and iodoacetic acid have been measured using osmometry and their values compared with the existing literature values obtained, usually, from conductometric measurements. Ionization constant determined by osmometry for the moderately strong weak acids were in reasonably good agreement with literature values. The results showed that two factors, the ionic strength and the osmotic coefficient, exert opposite effects in solutions of such weak acids. Another focus of the work was analytical chemistry students solution preparation skills. The prevailing teacher-structured experiments leave little room for students' ingenuity in quantitative volumetric analysis. The purpose of this part of the study was to improve students' skills in making solutions using instrument feedback in a constructivist-learning model. After making some solutions by weighing and dissolving solutes or by serial dilution, students used the spectrophotometer and the osmometer to compare their solutions with standard solutions. Students perceived the instrument feedback as a nonthreatening approach to monitoring the development of their skill levels and liked to clarify their understanding through interacting with an instructor-observer. An assessment of the instrument feedback and the constructivist model indicated that students would assume responsibility for their own learning if given the opportunity. This study involved 167 students enrolled in Quantitative Chemical

Nonradiative inter- and intramolecular energy transfer from the aromatic donor anisole to a synthesized photoswitchable acceptor system.

PubMed

Bardhan, Munmun; Bhattacharya, Sudeshna; Misra, Tapas; Mukhopadhyay, Rupa; De, Asish; Chowdhury, Joydeep; Ganguly, Tapan

2010-02-01

We report steady state and time resolved fluorescence measurements on acetonitrile (ACN) solutions of the model compounds, energy donor anisole (A) and a photoswitchable acceptor N,N'-1,2-phenylene di-p-tosylamide (B) and the multichromophore (M) where A and B are connected by a spacer containing both rigid triple (acetylenic) and flexible methylene bonds. Both steady state and time correlated single photon counting measurements demonstrate that though intermolecular energy transfer, of Forster type, between the donor and acceptor moieties occurs with rate 10(8)s(-1) but when these two reacting components are linked by a spacer (multichromophore, M) the observed transfer rate ( approximately 10(11)s(-1)) enhances. This seemingly indicates that the imposition of the spacer by inserting a triple bond may facilitate in the propagation of electronic excitation energy through bond. The time resolved fluorescence measurements along with the theoretical predictions using Configuration interaction singles (CIS) method by using 6-31G (d,p) basis set, implemented in the Gaussian package indicate the formations of the two excited conformers of B. The experimental findings made from the steady state and time resolved fluorescence measurements demonstrate that, though two different isomeric species of the acceptor B are formed in the excited singlet states, the prevailing singlet-singlet nonradiative energy transfer route was found from the donor A to the relatively longer-lived isomeric species of B. Copyright (c) 2009 Elsevier B.V. All rights reserved.

Group III Acceptors with Shallow and Deep Levels in Silicon Carbide: ESR and ENDOR Studies

NASA Astrophysics Data System (ADS)

Il'in, I. V.; Uspenskaya, Yu. A.; Kramushchenko, D. D.; Muzafarova, M. V.; Soltamov, V. A.; Mokhov, E. N.; Baranov, P. G.

2018-04-01

Results of investigations of Group III acceptors (B, Al, and Ga) in crystals of silicon carbide using the most informative electron spin resonance and electron nuclear double resonance methods are presented. Structural models of the acceptors with shallow and deep levels are considered. In addition to the data obtained earlier, studies using high-frequency magnetic resonance were obtained, which allowed revealing orthorhombic deviations from the axial symmetry for the deep acceptors; theoretical analysis explains experimentally found shifts of g factors for the deep acceptors arising due to the orthorhombic deviations, which appear probably due to the Jahn-Teller effect.

Optical Probing of Low-Pressure Solution Grown GaN Crystal Properties

DTIC Science & Technology

2010-04-01

observed in Mg and Si doped epitaxial films deposited by MBE and MOCVD on freestanding GaN HVPE substrates [23–25]. Considering the purity of the precursors...bands with similar energy positions here reported, a dominant deeper acceptor impurity has been assigned to Zn , a well known deep acceptor in GaN . Room...00-00-2010 to 00-00-2010 4. TITLE AND SUBTITLE Optical probing of low-pressure solution grown GaN crystal properties 5a. CONTRACT NUMBER 5b

Effects of topical oxiconazole and boric acid in alcohol solutions to rat inner ears.

PubMed

Özdemir, Süleyman; Tuncer, Ülkü; Tarkan, Özgür; Akar, Funda; Sürmelioğlu, Özgür

2013-06-01

The aim of this study is to evaluate the ototoxicity of topical oxiconazole and boric acid in alcohol solutions. Prospective controlled animal study. Research laboratory. Fifty adult Wistar albino rats were divided into 5 groups consisting of 10 animals each. The right tympanic membranes were perforated, and baseline and posttreatment distortion product otoacoustic emission (DPOAE) measurements were performed. The solutions were applied through the external ear canal to the middle ear twice a day for 14 days. The rats in group I and group II received 0.1 mL of oxiconazole-containing solution drops and 4% boric acid in alcohol solution drops, respectively. Group III received gentamicin solution (40 mg/mL) (ototoxic control), group IV received saline solution, and group V was followed without any medication. The baseline DPOAE results of the right ears of all animals tested were normal. Animals in groups I, II, IV, and V showed no statistically significant change in the DPOAE amplitudes. The rats in the gentamicin group showed a significant decrease. This study demonstrates that topically used oxiconazole and boric acid in alcohol solutions to the middle ear appear to be safe on the inner ear of rats. The safety of these drugs has not yet been confirmed in humans. Caution should be taken when prescribing these drugs, especially to patients who had tympanic membrane perforation. Ear drops should be chosen more carefully in an external ear infection for patients with tympanic membrane perforation to avoid ototoxicity.

High-Performance All-Polymer Solar Cells Achieved by Fused Perylenediimide-Based Conjugated Polymer Acceptors.

PubMed

Yin, Yuli; Yang, Jing; Guo, Fengyun; Zhou, Erjun; Zhao, Liancheng; Zhang, Yong

2018-05-09

We report three n-type polymeric electron acceptors (PFPDI-TT, PFPDI-T, and PFPDI-Se) based on the fused perylene diimide (FPDI) and thieno[3,2- b]thiophene, thiophene, or selenophene units for all-polymer solar cells (all-PSCs). These FPDI-based polymer acceptors exhibit strong absorption between 350 and 650 nm with wide optical bandgap of 1.86-1.91 eV, showing good absorption compensation with the narrow bandgap polymer donor. The lowest unoccupied molecular orbital (LUMO) energy levels were located at around -4.11 eV, which are comparable with those of the fullerene derivatives and other small molecular electron acceptors. The conventional all-PSCs based on the three polymer acceptors and PTB7-Th as polymer donor gave remarkable power conversion efficiencies (PCEs) of >6%, and the PFPDI-Se-based all-PSC achieved the highest PCE of 6.58% with a short-circuit current density ( J sc ) of 13.96 mA/cm 2 , an open-circuit voltage ( V oc ) of 0.76 V, and a fill factor (FF) of 62.0%. More interestingly, our results indicate that the photovoltaic performances of the FPDI-based polymer acceptors are mainly determined by the FPDI unit with a small effect from the comonomers, which is quite different from the others reported rylenediimide-based polymer acceptors. This intriguing phenomenon is speculated as the huge geometry configuration of the FPDI unit, which minimizes the effect of the comonomer. These results highlight a promising future for the application of the FPDI-based polymer acceptors in the highly efficient all-PSCs.

A theoretical probe on the non-covalent interactions of sulfadoxine drug with pi-acceptors

NASA Astrophysics Data System (ADS)

Sandhiya, L.; Senthilkumar, K.

2014-09-01

A detailed analysis of the interaction between an antimalarial drug sulfadoxine and four pi-acceptors, tetrachloro-catechol, picric acid, chloranil, and 2,3-dichloro-5,6-dicyano-1,4-benzoquinone is presented in this study. The interaction of the amine, amide, methoxy, Csbnd H groups and π electron density of the drug molecule with the acceptors are studied using DFT method at M06-2X level of theory with 6-31G(d,p) basis set. The interaction energy of the complexes is calculated using M06-2X, M06-HF, B3LYP-D and MP2 methods with 6-31G(d,p) basis set. The role of weak interactions on the formation and stability of the complexes is discussed in detail. The two aromatic platforms of sulfadoxine play a major role in determining the stability of the complexes. The electron density difference maps have been plotted for the most stable drug interacting complexes to understand the changes in electron density delocalization upon the complex formation. The nature of the non-covalent interaction has been addressed from NCI plot. The infrared spectra calculated at M06-2X/6-31G(d,p) level of theory is used to characterize the most stable complexes. The SDOX-pi acceptor complexation leads to characteristic changes in the NMR spectra. The 13C, 1H, 17O and 15N NMR chemical shifts have been calculated using GIAO method at M06-2X/6-311+G(d,p)//M06-2X/6-31G(d,p) level of theory. The results obtained from this study confirm the role of non-covalent interactions on the function of the sulfadoxine drug.

Investigation of the donor and acceptor range for chiral carboligation catalyzed by the E1 component of the 2-oxoglutarate dehydrogenase complex

PubMed Central

Patel, Hetalben; Shim, Da Jeong; Farinas, Edgardo T.; Jordan, Frank

2013-01-01

The potential of thiamin diphosphate (ThDP)-dependent enzymes to catalyze C-C bond forming (carboligase) reactions with high enantiomeric excess has been recognized for many years. Here we report the application of the E1 component of the Escherichia coli 2-oxoglutarate dehydrogenase multienzyme complex in the synthesis of chiral compounds with multiple functional groups in good yield and high enantiomeric excess, by varying both the donor substrate (different 2-oxo acids) and the acceptor substrate (glyoxylate, ethyl glyoxylate and methyl glyoxal). Major findings include the demonstration that the enzyme can accept 2-oxovalerate and 2-oxoisovalerate in addition to its natural substrate 2-oxoglutarate, and that the tested acceptors are also acceptable in the carboligation reaction, thereby very much expanding the repertory of the enzyme in chiral synthesis. PMID:24277992

Enhanced biodegradation of cyclotetramethylenetetranitramine (HMX) under mixed electron-acceptor condition.

PubMed

Boopathy, R

2001-02-01

The biodegradation of cyclotetramethylenetetranitramine, commonly known as 'high melting explosive' (HMX), under various electron-acceptor conditions was investigated using enrichment cultures developed from the anaerobic digester sludge of Thibodaux sewage treatment plant. The results indicated that the HMX was biodegraded under sulfate reducing, nitrate reducing, fermenting, methanogenic, and mixed electron accepting conditions. However, the rates of degradation varied among the various conditions studied. The fastest removal of HMX (from 22 ppm on day 0 to < 0.05 ppm on day 11) was observed under mixed electron-acceptor conditions, followed in order by sulfate reducing, fermenting, methanogenic, and nitrate reducing conditions. Under aerobic conditions, HMX was not biodegraded, which indicated that HMX degradation takes place under anaerobic conditions via reduction. HMX was converted to methanol and chloroform under mixed electron-acceptor conditions. This study showed evidence for HMX degradation under anaerobic conditions in a mixed microbial population system similar to any contaminated field sites, where a heterogeneous population exists.

Uptake of Hypobromous Acid (HOBr) by Aqueous Sulfuric Acid Solutions: Low-Temperature Solubility and Reaction

NASA Technical Reports Server (NTRS)

Iraci, Laura T.; Michelsen, Rebecca R.; Ashbourn, Samatha F. M.; Rammer, Thomas A.; Golden, David M.

2005-01-01

Hypobromous acid (HOBr) is a key species linking inorganic bromine to the chlorine and odd hydrogen chemical families. We have measured the solubility of HOBr in 45 - 70 wt% sulfuric acid solutions representative of upper tropospheric and lower stratospheric aerosol composition. Over the temperature range 201 - 252 K, HOBr is quite soluble in sulfuric acid, with an effective Henry's law coefficient, H* = 10(exp 4) - 10(exp 7) mol/L/atm. H* is inversely dependent on temperature, with Delta H = -46.2 kJ/mol and Delta S = -106.2 J/mol/K for 55 - 70 wt% H2SO4 solutions. Our study includes temperatures which overlap both previous measurements of HOBr solubility. For uptake into aqueous 45 wt% H2SO4, the solubility can be described by log H* = 3665/T - 10.63. For 55 - 70 wt% H2SO4, log H* = 2412/T - 5.55. At temperatures colder than approx. 213 K, the solubility of HOBr in 45 wt% H2SO4 is noticeably larger than in 70 wt% H2SO4. The solubility of HOBr is comparable to that of HBr, indicating that upper tropospheric and lower stratospheric aerosols should contain equilibrium concentrations of HOBr which equal or exceed those of HBr. Our measurements indicate chemical reaction of HOBr upon uptake into aqueous sulfuric acid in the presence of other brominated gases followed by evolution of gaseous products including Br2O and Br2, particularly at 70 wt% H2SO4.

Liquid Superlubricity of Polyethylene Glycol Aqueous Solution Achieved with Boric Acid Additive.

PubMed

Ge, Xiangyu; Li, Jinjin; Zhang, Chenhui; Luo, Jianbin

2018-03-27

Boric acid is a weak acid and has been used as a lubrication additive because of its special structure. In this study, we report that boric acid could achieve a robust superlubricity (μ < 0.01) as an additive in polyethylene glycol (PEG) aqueous solution at the Si 3 N 4 /SiO 2 interfaces. The superlow and steady friction coefficient of approximately 0.004-0.006 could be achieved with boric acid under neutral conditions (pH of approximately 6.4), which is different from the acidic conditions leading to superlubricity. The influence of various factors, including boric acid concentration, sliding speed, applied load, PEG molecular weight, and the volume of lubricant on the superlubricity, were investigated. The results reveal that the PEG aqueous solution with the boric acid additive could achieve superlubricity under a wide range of conditions. The surface composition analysis shows that the synergy effect between boric acid and PEG provides sufficient H + ions to realize the running-in process. Moreover, a composite tribochemical film composed of silica and ammonia-containing compounds were formed on the ball surface, contributing to the superlubricity. The film thickness calculation shows that superlubricity was achieved in a mixed lubrication region, and therefore, the superlubricity state was dominated by both the composite tribochemical film formed via the tribochemical reaction on the contact surfaces and the hydrodynamic lubricating film between the contact surfaces. Such a liquid superlubricity achieved under neutral conditions is of importance for both scientific understanding and engineering applications.

High-Yield Production of Levulinic Acid from Pretreated Cow Dung in Dilute Acid Aqueous Solution.

PubMed

Su, Jialei; Shen, Feng; Qiu, Mo; Qi, Xinhua

2017-02-14

Agricultural waste cow dung was used as feedstock for the production of a high value-added chemical levulinic acid (LA) in dilute acid aqueous solutions. A high LA yield of 338.9 g/kg was obtained from the pretreated cow dung, which was much higher than that obtained from the crude cow dung (135 g/kg), mainly attributed to the breakage of the lignin fraction in the lignocellulose structure of the cow dung by potassium hydroxide (KOH) pretreatment, and thus enhanced the accessibility of cow dung to the acid sites in the catalytic reaction. Meanwhile, another value-added chemical formic acid could be obtained with a yield of ca. 160 g/kg in the process, implying a total production of ca. 500 g/kg yield for LA and formic acid from the pretreated cow dung with the proposed process. The developed process was shown to be tolerant to high initial substrate loading with a satisfied LA yield. This work provides a promising strategy for the value-increment utilization of liglocellulosic agricultural residues.

Influence of trace elements on stabilization of aqueous solutions of ascorbic acid.

PubMed

Dolińska, Barbara; Ostróżka-Cieślik, Aneta; Caban, Artur; Rimantas, Klimas; Leszczyńska, Lucyna; Ryszka, Florian

2012-12-01

Together with vitamin C, zinc, selenium, manganese, and magnesium play a vital role in the preservation of organs scheduled for transplantation. In the present study, it is shown that addition of 1 mg/l of these elements influences the stability of 0.3 mM ascorbic acid solutions. The solution's stability was estimated using an accelerated stability test. The concentration of vitamin C was measured using a validated spectrophotometric method, which uses the reduction of 2,6-dichlorophenoloindophenol by ascorbic acid. Elevated temperatures, the factor accelerating substances' decomposition reaction rate, were used in the tests. The research was conducted at two temperatures at intervals of 10 °C: 80 ± 0.1 and 90 ± 0.1 °C. It was stated that the studied substances' decomposition occurred in accordance with the equation for first-order reactions. The function of the logarithmic concentration (log%C) over time was revealed to be rectilinear. This dependence was used to determine the kinetics of decomposition reaction rate parameters. The stabilization of vitamin C solutions was measured as the time in which 10 % of the substance decomposed at 20 and 0 °C. Addition of Se(IV) or Mg(II) ions significantly increase the stability of ascorbic acid solution (∼34 and ∼16 %, respectively), but Zn(II) causes a significant decrease in stability by ∼23 %. Addition of Mn(II) has no significant influence on vitamin C stability.

Solvent as electron donor: Donor/acceptor electronic coupling is a dynamical variable

DOE Office of Scientific and Technical Information (OSTI.GOV)

Castner, E.W. Jr.; Kennedy, D.; Cave, R.J.

2000-04-06

The authors combine analysis of measurements by femtosecond optical spectroscopy, computer simulations, and the generalized Mulliken-Hush (GMH) theory in the study of electron-transfer reactions and electron donor-acceptor interactions. The study focus is on ultrafast photoinduced electron-transfer reactions from aromatic amine solvent donors to excited-state acceptors. The experimental results from femtosecond dynamical measurements fall into three categories: six coumarin acceptors reductively quenched by N,N-dimethylaniline (DMA), eight electron-donating amine solvents reductively quenching coumarin 152 (7-(dimethylamino)-4-(trifluoromethyl)-coumarin), and reductive quenching dynamics of two coumarins by DMA as a function of dilution in the nonreactive solvents toluene and chlorobenzene. Applying a combination of molecular dynamicsmore » trajectories, semiempirical quantum mechanical calculations (of the relevant adiabatic electronic states), and GMH theory to the C152/DMA photoreaction, the authors calculate the electron donor/acceptor interaction parameter H{sub DA} at various time frames, H{sub DA} is strongly modulated by both inner-sphere and outer-sphere nuclear dynamics, leading us to conclude that H{sub DA} must be considered as a dynamical variable.« less

Micellar electrokinetic chromatography with acid labile surfactant.

PubMed

Stanley, Bob; Lucy, Charles A

2012-02-24

We present a study of a degradable surfactant, sodium 4-[(2-methyl-2-undecyl-1,3-dioxolan-4-yl)methoxy]-1-propane sulfonate that is also known as an acid-labile surfactant (ALS). The performance of ALS as a pseudostationary phase is assessed and compared with established pseudostationary phases such as sodium dodecyl sulphate (SDS), volatile surfactants and polymeric micelles. ALS achieves separation efficiency of 100,000-145,000 theoretical plates and relative standard deviation (RSD) of electrophoretic mobility (n=5) of less than 3%. Retention factors with ALS are strongly correlated with those with SDS. This is shown by the R2=0.79 for all eleven analytes and an R2=0.992 for specifically the non-hydrogen bonding (NHB) analytes. However, ALS displays different selectivity than SDS for hydrogen bond donor (HBD) and hydrogen bond acceptor (HBA) solutes (R2 of 0.74 and 0.88, respectively). ALS is degraded to less surface active compounds in acidic solution. These less surface-active compounds are more compatible with the electrospray ionization mass spectrometry (ESI-MS). ALS has a half-life of 48 min at pH 4. ALS has the potential to couple micellar electrokinetic chromatography (MEKC) with the ESI-MS. ALS can be used as a pseudostationary phase for a high efficiency separation and later acid hydrolyzed to enable an ESI-MS analysis. Copyright © 2011 Elsevier B.V. All rights reserved.

Molecular dynamics simulation studies of the interactions between ionic liquids and amino acids in aqueous solution.

PubMed

Tomé, Luciana I N; Jorge, Miguel; Gomes, José R B; Coutinho, João A P

2012-02-16

Although the understanding of the influence of ionic liquids (ILs) on the solubility behavior of biomolecules in aqueous solutions is relevant for the design and optimization of novel biotechnological processes, the underlying molecular-level mechanisms are not yet consensual or clearly elucidated. In order to contribute to the understanding of the molecular interactions established between amino acids and ILs in aqueous media, classical molecular dynamics (MD) simulations were performed for aqueous solutions of five amino acids with different structural characteristics (glycine, alanine, valine, isoleucine, and glutamic acid) in the presence of 1-butyl-3-methylimidazolium bis(trifluoromethyl)sulfonyl imide. The results from MD simulations enable to relate the properties of the amino acids, namely their hydrophobicity, to the type and strength of their interactions with ILs in aqueous solutions and provide an explanation for the direction and magnitude of the solubility phenomena observed in [IL + amino acid + water] systems by a mechanism governed by a balance between competitive interactions of the IL cation, IL anion, and water with the amino acids.

Nitrogen Oxides in Early Earth's Atmosphere as Electron Acceptors for Life's Emergence.

PubMed

Wong, Michael L; Charnay, Benjamin D; Gao, Peter; Yung, Yuk L; Russell, Michael J

2017-10-01

We quantify the amount of nitrogen oxides (NOx) produced through lightning and photochemical processes in the Hadean atmosphere to be available in the Hadean ocean for the emergence of life. Atmospherically generated nitrate (NO 3 - ) and nitrite (NO 2 - ) are the most attractive high-potential electron acceptors for pulling and enabling crucial redox reactions of autotrophic metabolic pathways at submarine alkaline hydrothermal vents. The Hadean atmosphere, dominated by CO 2 and N 2 , will produce nitric oxide (NO) when shocked by lightning. Photochemical reactions involving NO and H 2 O vapor will then produce acids such as HNO, HNO 2 , HNO 3 , and HO 2 NO 2 that rain into the ocean. There, they dissociate into or react to form nitrate and nitrite. We present new calculations based on a novel combination of early-Earth global climate model and photochemical modeling, and we predict the flux of NOx to the Hadean ocean. In our 0.1-, 1-, and 10-bar pCO 2 models, we calculate the NOx delivery to be 2.4 × 10 5 , 6.5 × 10 8 , and 1.9 × 10 8 molecules cm -2 s -1 . After only tens of thousands to tens of millions of years, these NOx fluxes are expected to produce sufficient (micromolar) ocean concentrations of high-potential electron acceptors for the emergence of life. Key Words: Nitrogen oxides-Nitrate-Nitrite-Photochemistry-Lightning-Emergence of life. Astrobiology 17, 975-983.

Revisiting the operational RNA code for amino acids: Ensemble attributes and their implications.

PubMed

Shaul, Shaul; Berel, Dror; Benjamini, Yoav; Graur, Dan

2010-01-01

It has been suggested that tRNA acceptor stems specify an operational RNA code for amino acids. In the last 20 years several attributes of the putative code have been elucidated for a small number of model organisms. To gain insight about the ensemble attributes of the code, we analyzed 4925 tRNA sequences from 102 bacterial and 21 archaeal species. Here, we used a classification and regression tree (CART) methodology, and we found that the degrees of degeneracy or specificity of the RNA codes in both Archaea and Bacteria differ from those of the genetic code. We found instances of taxon-specific alternative codes, i.e., identical acceptor stem determinants encrypting different amino acids in different species, as well as instances of ambiguity, i.e., identical acceptor stem determinants encrypting two or more amino acids in the same species. When partitioning the data by class of synthetase, the degree of code ambiguity was significantly reduced. In cryptographic terms, a plausible interpretation of this result is that the class distinction in synthetases is an essential part of the decryption rules for resolving the subset of RNA code ambiguities enciphered by identical acceptor stem determinants of tRNAs acylated by enzymes belonging to the two classes. In evolutionary terms, our findings lend support to the notion that in the pre-DNA world, interactions between tRNA acceptor stems and synthetases formed the basis for the distinction between the two classes; hence, ambiguities in the ancient RNA code were pivotal for the fixation of these enzymes in the genomes of ancestral prokaryotes.

Revisiting the operational RNA code for amino acids: Ensemble attributes and their implications

PubMed Central

Shaul, Shaul; Berel, Dror; Benjamini, Yoav; Graur, Dan

2010-01-01

It has been suggested that tRNA acceptor stems specify an operational RNA code for amino acids. In the last 20 years several attributes of the putative code have been elucidated for a small number of model organisms. To gain insight about the ensemble attributes of the code, we analyzed 4925 tRNA sequences from 102 bacterial and 21 archaeal species. Here, we used a classification and regression tree (CART) methodology, and we found that the degrees of degeneracy or specificity of the RNA codes in both Archaea and Bacteria differ from those of the genetic code. We found instances of taxon-specific alternative codes, i.e., identical acceptor stem determinants encrypting different amino acids in different species, as well as instances of ambiguity, i.e., identical acceptor stem determinants encrypting two or more amino acids in the same species. When partitioning the data by class of synthetase, the degree of code ambiguity was significantly reduced. In cryptographic terms, a plausible interpretation of this result is that the class distinction in synthetases is an essential part of the decryption rules for resolving the subset of RNA code ambiguities enciphered by identical acceptor stem determinants of tRNAs acylated by enzymes belonging to the two classes. In evolutionary terms, our findings lend support to the notion that in the pre-DNA world, interactions between tRNA acceptor stems and synthetases formed the basis for the distinction between the two classes; hence, ambiguities in the ancient RNA code were pivotal for the fixation of these enzymes in the genomes of ancestral prokaryotes. PMID:19952117

Arsenic removal from acidic solutions with biogenic ferric precipitates.

PubMed

Ahoranta, Sarita H; Kokko, Marika E; Papirio, Stefano; Özkaya, Bestamin; Puhakka, Jaakko A

2016-04-05

Treatment of acidic solution containing 5g/L of Fe(II) and 10mg/L of As(III) was studied in a system consisting of a biological fluidized-bed reactor (FBR) for iron oxidation, and a gravity settler for iron precipitation and separation of the ferric precipitates. At pH 3.0 and FBR retention time of 5.7h, 96-98% of the added Fe(II) precipitated (99.1% of which was jarosite). The highest iron oxidation and precipitation rates were 1070 and 28mg/L/h, respectively, and were achieved at pH 3.0. Subsequently, the effect of pH on arsenic removal through sorption and/or co-precipitation was examined by gradually decreasing solution pH from 3.0 to 1.6 (feed pH). At pH 3.0, 2.4 and 1.6, the highest arsenic removal efficiencies obtained were 99.5%, 80.1% and 7.1%, respectively. As the system had ferric precipitates in excess, decreased arsenic removal was likely due to reduced co-precipitation at pH<2.4. As(III) was partially oxidized to As(V) in the system. In shake flask experiments, As(V) sorbed onto jarosite better than As(III). Moreover, the sorption capacity of biogenic jarosite was significantly higher than that of synthetic jarosite. The developed bioprocess simultaneously and efficiently removes iron and arsenic from acidic solutions, indicating potential for mining wastewater treatment. Copyright © 2015 Elsevier B.V. All rights reserved.

Single molecule-level study of donor-acceptor interactions and nanoscale environment in blends

NASA Astrophysics Data System (ADS)

Quist, Nicole; Grollman, Rebecca; Rath, Jeremy; Robertson, Alex; Haley, Michael; Anthony, John; Ostroverkhova, Oksana

2017-02-01

Organic semiconductors have attracted considerable attention due to their applications in low-cost (opto)electronic devices. The most successful organic materials for applications that rely on charge carrier generation, such as solar cells, utilize blends of several types of molecules. In blends, the local environment strongly influences exciton and charge carrier dynamics. However, relationship between nanoscale features and photophysics is difficult to establish due to the lack of necessary spatial resolution. We use functionalized fluorinated pentacene (Pn) molecule as single molecule probes of intermolecular interactions and of the nanoscale environment in blends containing donor and acceptor molecules. Single Pn donor (D) molecules were imaged in PMMA in the presence of acceptor (A) molecules using wide-field fluorescence microscopy. Two sample configurations were realized: (i) a fixed concentration of Pn donor molecules, with increasing concentration of acceptor molecules (functionalized indenflouorene or PCBM) and (ii) a fixed concentration of acceptor molecules with an increased concentration of the Pn donor. The D-A energy transfer and changes in the donor emission due to those in the acceptor- modified polymer morphology were quantified. The increase in the acceptor concentration was accompanied by enhanced photobleaching and blinking of the Pn donor molecules. To better understand the underlying physics of these processes, we modeled photoexcited electron dynamics using Monte Carlo simulations. The simulated blinking dynamics were then compared to our experimental data, and the changes in the transition rates were related to the changes in the nanoscale environment. Our study provides insight into evolution of nanoscale environment during the formation of bulk heterojunctions.

Sterilisation: characteristics of vasectomy acceptors in Delhi.

PubMed

Sarkar, N N

1993-01-01

The place of vasectomy within the sterilisation programme in Delhi over the period 1983-88 is reviewed and data on vasectomy acceptance and characteristics of acceptors are analysed. Findings suggest a need to improve the strategy for the promotion of vasectomy within the metropolis.

Thermodynamic characteristics of the interaction between nicotinic acid and phenylalanine in an aqueous buffer solution at 298 K

NASA Astrophysics Data System (ADS)

Badelin, V. G.; Tyunina, E. Yu.; Mezhevoi, I. N.; Tarasova, G. N.

2013-08-01

The interaction between L-phenylalanine and nicotinic acid is studied by solution calorimetry in an aqueous buffer solution (pH 7.35) at different ratios of the reagents. Experimental data on the enthalpy of dissolution of amino acid in the buffer solution of nicotinic acid at 298.15 K are calculated. The values of thermodynamic parameters for the complexation of L-phenylalanine with nicotinic acid are calculated. It is shown that the formation of a 1: 2 molecular complex is stabilized by the entropy factor due to the dominant role of the dehydration effect of initial reagents.

Mechanisms of electron acceptor utilization: Implications for simulating anaerobic biodegradation

USGS Publications Warehouse

Schreiber, M.E.; Carey, G.R.; Feinstein, D.T.; Bahr, J.M.

2004-01-01

Simulation of biodegradation reactions within a reactive transport framework requires information on mechanisms of terminal electron acceptor processes (TEAPs). In initial modeling efforts, TEAPs were approximated as occurring sequentially, with the highest energy-yielding electron acceptors (e.g. oxygen) consumed before those that yield less energy (e.g., sulfate). Within this framework in a steady state plume, sequential electron acceptor utilization would theoretically produce methane at an organic-rich source and Fe(II) further downgradient, resulting in a limited zone of Fe(II) and methane overlap. However, contaminant plumes often display much more extensive zones of overlapping Fe(II) and methane. The extensive overlap could be caused by several abiotic and biotic processes including vertical mixing of byproducts in long-screened monitoring wells, adsorption of Fe(II) onto aquifer solids, or microscale heterogeneity in Fe(III) concentrations. Alternatively, the overlap could be due to simultaneous utilization of terminal electron acceptors. Because biodegradation rates are controlled by TEAPs, evaluating the mechanisms of electron acceptor utilization is critical for improving prediction of contaminant mass losses due to biodegradation. Using BioRedox-MT3DMS, a three-dimensional, multi-species reactive transport code, we simulated the current configurations of a BTEX plume and TEAP zones at a petroleum- contaminated field site in Wisconsin. Simulation results suggest that BTEX mass loss due to biodegradation is greatest under oxygen-reducing conditions, with smaller but similar contributions to mass loss from biodegradation under Fe(III)-reducing, sulfate-reducing, and methanogenic conditions. Results of sensitivity calculations document that BTEX losses due to biodegradation are most sensitive to the age of the plume, while the shape of the BTEX plume is most sensitive to effective porosity and rate constants for biodegradation under Fe(III)-reducing and

Bacterial manganese reduction and growth with manganese oxide as the sole electron acceptor

NASA Technical Reports Server (NTRS)

Myers, Charles R.; Nealson, Kenneth H.

1988-01-01

Microbes that couple growth to the reduction of manganese could play an important role in the biogeochemistry of certain anaerobic environments. Such a bacterium, Alteromonas putrefaciens MR-1, couples its growth to the reduction of manganese oxides only under anaerobic conditions. The characteristics of this reduction are consistent with a biological, and not an indirect chemical, reduction of manganese, which suggest that this bacterium uses manganic oxide as a terminal electron acceptor. It can also utilize a large number of other compounds as terminal electron acceptors; this versatility could provide a distinct advantage in environments where electron-acceptor concentrations may vary.

Highly regioselective Lewis acid-catalyzed [3+2] cycloaddition of alkynes with donor-acceptor oxiranes by selective carbon-carbon bond cleavage of epoxides.

PubMed

Liu, Renrong; Zhang, Mei; Zhang, Junliang

2011-12-28

A novel, efficient, highly regioselective Sc(OTf)(3)-catalyzed [3+2] cycloaddition of electron-rich alkynes with donor-acceptor oxiranes via highly chemoselective C-C bond cleavage under mild conditions was developed. This journal is © The Royal Society of Chemistry 2011

The response of soil solution chemistry in European forests to decreasing acid deposition.

PubMed

Johnson, James; Graf Pannatier, Elisabeth; Carnicelli, Stefano; Cecchini, Guia; Clarke, Nicholas; Cools, Nathalie; Hansen, Karin; Meesenburg, Henning; Nieminen, Tiina M; Pihl-Karlsson, Gunilla; Titeux, Hugues; Vanguelova, Elena; Verstraeten, Arne; Vesterdal, Lars; Waldner, Peter; Jonard, Mathieu

2018-03-31

Acid deposition arising from sulphur (S) and nitrogen (N) emissions from fossil fuel combustion and agriculture has contributed to the acidification of terrestrial ecosystems in many regions globally. However, in Europe and North America, S deposition has greatly decreased in recent decades due to emissions controls. In this study, we assessed the response of soil solution chemistry in mineral horizons of European forests to these changes. Trends in pH, acid neutralizing capacity (ANC), major ions, total aluminium (Al tot ) and dissolved organic carbon were determined for the period 1995-2012. Plots with at least 10 years of observations from the ICP Forests monitoring network were used. Trends were assessed for the upper mineral soil (10-20 cm, 104 plots) and subsoil (40-80 cm, 162 plots). There was a large decrease in the concentration of sulphate (SO42-) in soil solution; over a 10-year period (2000-2010), SO42- decreased by 52% at 10-20 cm and 40% at 40-80 cm. Nitrate was unchanged at 10-20 cm but decreased at 40-80 cm. The decrease in acid anions was accompanied by a large and significant decrease in the concentration of the nutrient base cations: calcium, magnesium and potassium (Bc = Ca 2+  + Mg 2+  + K + ) and Al tot over the entire dataset. The response of soil solution acidity was nonuniform. At 10-20 cm, ANC increased in acid-sensitive soils (base saturation ≤10%) indicating a recovery, but ANC decreased in soils with base saturation >10%. At 40-80 cm, ANC remained unchanged in acid-sensitive soils (base saturation ≤20%, pHCaCl2 ≤ 4.5) and decreased in better-buffered soils (base saturation >20%, pHCaCl2 > 4.5). In addition, the molar ratio of Bc to Al tot either did not change or decreased. The results suggest a long-time lag between emission abatement and changes in soil solution acidity and underline the importance of long-term monitoring in evaluating ecosystem response to decreases in deposition. © 2018 John Wiley & Sons

Infrared optical constants of H2O ice, amorphous nitric acid solutions, and nitric acid hydrates

NASA Technical Reports Server (NTRS)

Toon, Owen B.; Koehler, Birgit G.; Middlebrook, Ann M.; Tolbert, Margaret A.; Jordon, Joseph

1994-01-01

We determined the infrared optical constants of nitric acid trihydrate, nitric acid dihydrate, nitric acid monohydrate, and solid amorphous nitric acid solutions which crystallize to form these hydrates. We have also found the infrared optical constants of H2O ice. We measured the transmission of infrared light throught thin films of varying thickness over the frequency range from about 7000 to 500/cm at temperatures below 200 K. We developed a theory for the transmission of light through a substrate that has thin films on both sides. We used an iterative Kramers-Kronig technique to determine the optical constants which gave the best match between measured transmission spectra and those calculated for a variety of films of different thickness. These optical constants should be useful for calculations of the infrared spectrum of polar stratospheric clouds.

Assessment of the Effects Exerted by Acid and Alkaline Solutions on Bone: Is Chemistry the Answer?

PubMed

Amadasi, Alberto; Camici, Arianna; Porta, Davide; Cucca, Lucia; Merli, Daniele; Milanese, Chiara; Profumo, Antonella; Rassifi, Nabila; Cattaneo, Cristina

2017-09-01

The treatment of corpses with extremely acid or basic liquids is sometimes performed in criminal contexts. A thorough characterization by chemical analysis may provide further help to macroscopic and microscopic analysis; 63 porcine bone samples were treated with solutions at different pH (1-14) for immersion periods up to 70 days, as well as in extremely acidic sulfuric acid solutions (9 M/18 M) and extremely basic sodium hydroxide. Inductively coupled optical emission spectrometry (ICP-OES)/plasma mass spectrometry (ICP-MS), Fourier transform infrared spectroscopy (FT-IR), energy dispersive X-ray analysis (EDX), X-ray powder diffraction (XRPD), and scanning electron microscopy (SEM) showed that only the sulfuric acid solution 18 M was able to completely dissolve the sample. In addition, chemical analysis allowed to recognize the contact between bone and substances. Hydrated calcium sulfate arose from extreme pH. The possibility of detecting the presence of human material within the residual solution was demonstrated, especially with FT-IR, ICP-OES, and EDX. © 2017 American Academy of Forensic Sciences.

Thermodynamics of Hydrophobic Amino Acids in Solution: A Combined Experimental–Computational Study

DOE PAGES

Song, Lingshuang; Yang, Lin; Meng, Jie; ...

2016-12-29

Here, we present a joint experimental-computational study to quantitatively describe the thermodynamics of hydrophobic leucine amino acids in aqueous solution. X-ray scattering data were acquired at a series of solute and salt concentrations to effectively measure inter-leucine interactions, indicating that a major scattering peak is observed consistently at q = 0.83 Å -1. Atomistic molecular dynamics simulations were then performed and compared with the scattering data, achieving high consistency at both small and wider scattering angles (q = 0$-$1.5 Å -1). This experimental-computational consistence enables a first glimpse of the leucineleucine interacting landscape, where two leucine molecules are aligned mostlymore » in a parallel fashion, as opposed to anti-parallel, but also allows us to derive effective leucine-leucine interactions in solution. Collectively, this combined approach of employing experimental scattering and molecular simulation enables a quantitative characterization on effective inter-molecular interactions of hydrophobic amino acids, critical for protein function and dynamics such as protein folding.« less

Thermodynamics of Hydrophobic Amino Acids in Solution: A Combined Experimental–Computational Study

DOE Office of Scientific and Technical Information (OSTI.GOV)

Song, Lingshuang; Yang, Lin; Meng, Jie

Here, we present a joint experimental-computational study to quantitatively describe the thermodynamics of hydrophobic leucine amino acids in aqueous solution. X-ray scattering data were acquired at a series of solute and salt concentrations to effectively measure inter-leucine interactions, indicating that a major scattering peak is observed consistently at q = 0.83 Å -1. Atomistic molecular dynamics simulations were then performed and compared with the scattering data, achieving high consistency at both small and wider scattering angles (q = 0$-$1.5 Å -1). This experimental-computational consistence enables a first glimpse of the leucineleucine interacting landscape, where two leucine molecules are aligned mostlymore » in a parallel fashion, as opposed to anti-parallel, but also allows us to derive effective leucine-leucine interactions in solution. Collectively, this combined approach of employing experimental scattering and molecular simulation enables a quantitative characterization on effective inter-molecular interactions of hydrophobic amino acids, critical for protein function and dynamics such as protein folding.« less

Nanostructural characterization of large-scale porous alumina fabricated via anodizing in arsenic acid solution

NASA Astrophysics Data System (ADS)

Akiya, Shunta; Kikuchi, Tatsuya; Natsui, Shungo; Suzuki, Ryosuke O.

2017-05-01

Anodizing of aluminum in an arsenic acid solution is reported for the fabrication of anodic porous alumina. The highest potential difference (voltage) without oxide burning increased as the temperature and the concentration of the arsenic acid solution decreased, and a high anodizing potential difference of 340 V was achieved. An ordered porous alumina with several tens of cells was formed in 0.1-0.5 M arsenic acid solutions at 310-340 V for 20 h. However, the regularity of the porous alumina was not improved via anodizing for 72 h. No pore sealing behavior of the porous alumina was observed upon immersion in boiling distilled water, and it may be due to the formation of an insoluble complex on the oxide surface. The porous alumina consisted of two different layers: a hexagonal alumina layer that contained arsenic from the electrolyte and a pure alumina honeycomb skeleton. The porous alumina exhibited a white photoluminescence emission at approximately 515 nm under UV irradiation at 254 nm.

Acceptor-type hydroxide graphite intercalation compounds electrochemically formed in high ionic strength solutions.

PubMed

Miyazaki, Kohei; Iizuka, Asuka; Mikata, Koji; Fukutsuka, Tomokazu; Abe, Takeshi

2017-09-05

The intercalation of hydroxide ions (OH - ) into graphite formed graphite intercalation compounds (GICs) in high ionic strength solutions. GICs of solvated OH - anions with two water molecules (OH - ·2H 2 O) in alkaline aqueous solutions and GICs of only OH - anions in a molten NaOH-KOH salt solution were electrochemically synthesized.

A study on lithium/air secondary batteries-Stability of NASICON-type glass ceramics in acid solutions

NASA Astrophysics Data System (ADS)

Shimonishi, Y.; Zhang, T.; Johnson, P.; Imanishi, N.; Hirano, A.; Takeda, Y.; Yamamoto, O.; Sammes, N.

The stability of a NASICON-type lithium ion conducting solid electrolyte, Li 1+ x+ yTi 2- xAl xP 3- ySi yO 12 (LTAP), in acetic acid and formic acid solutions was examined. XRD patterns of the LTAP powders immersed in 100% acetic acid and formic acid at 50 °C for 4 months showed no change as compared to the pristine LTAP. However, the electrical conductivity of LTAP drastically decreased. On the other hand, no significant electrical conductivity change of LTAP immersed in lithium formate saturated formic acid-water solution was observed, and the electrical conductivity of LTAP immersed in lithium acetate saturated acetic acid-water increased. Cyclic voltammogram tests suggested that acetic acid was stable up to a high potential, but formic acid decomposed under the decomposition potential of water. The acetic acid solution was considered to be a candidate for the active material in the air electrode of lithium-air rechargeable batteries. The cell reaction was considered as 2Li + 2 CH 3COOH + 1/2O 2 = 2CH 3COOLi + H 2O. The energy density of this lithium-air system is calculated to be 1477 Wh kg -1 from the weights of Li and CH 3COOH, and an observed open-circuit voltage of 3.69 V.

Mechanistic study of fulvic acid assisted propranolol photodegradation in aqueous solution.

PubMed

Makunina, Maria P; Pozdnyakov, Ivan P; Chen, Yong; Grivin, Vyacheslav P; Bazhin, Nikolay M; Plyusnin, Victor F

2015-01-01

Laser flash (355 nm) and stationary (365 nm) photolysis were used to study the mechanisms of propranolol photolysis in the presence of fulvic acid in aqueous solutions. The FA-assisted photodegradation of propranolol was observed using UV-A irradiation (where propranolol is stable). Direct evidence indicated that the photodegradation resulted from the static quenching of the FA triplet state by propranolol via the electron transfer mechanism. The triplet state yield (ϕT≈0.6%) and the T-T absorption coefficient (ɛT(620 nm)≈5×10(4) M(-1) cm(-1)) were estimated for the first time by modeling the yields of the FA triplet state in the presence of propranolol. Thus, fulvic acid is a promising agent for accelerating propranolol photodegradation in aqueous solutions under UV-A light irradiation. Copyright © 2014 Elsevier Ltd. All rights reserved.

Chemical Corrosion of Liquid-Phase Sintered SiC in Acidic/Alkaline Solutions Part 1. Corrosion in HNO3 Solution

NASA Astrophysics Data System (ADS)

Zhang, Lei; Zhang, Ming; He, Xinnong; Tang, Wenming

2016-03-01

The corrosion behavior of the liquid-phase sintered SiC (LPS-SiC) was studied by dipping in 3.53 mol/L HNO3 aqueous solution at room temperature and 70 °C, respectively. The weight loss, strength reduction and morphology evolution of the SiC specimens during corroding were revealed and also the chemical corrosion process and mechanism of the SiC specimens in the acidic solution were clarified. The results show that the corrosion of the LPS-SiC specimens in the HNO3 solution is selective. The SiC particles are almost free from corrosion, but the secondary phases of BaAl2Si2O8 (BAS) and Y2Si2O7 are corroded via an acid-alkali neutralization reaction. BAS has a higher corrosion rate than Y2Si2O7, resulting in the formation of the bamboo-leaf-like corrosion pits. As the SiC specimens etched in the HNO3 solution at room temperature for 75 days, about 80 μm thickness corrosion layer forms. The weight loss and bending strength reduction of the etched SiC specimens are 2.6 mg/cm2 and 52%, respectively. The corrosion of the SiC specimens is accelerated in the 70 °C HNO3 solution with a rate about five times bigger than that in the same corrosion medium at room temperature.

Triplet Tellurophene-Based Acceptors for Organic Solar Cells.

PubMed

Yang, Lei; Gu, Wenxing; Lv, Lei; Chen, Yusheng; Yang, Yufei; Ye, Pan; Wu, Jianfei; Hong, Ling; Peng, Aidong; Huang, Hui

2018-01-22

Triplet materials have been employed to achieve high-performing organic solar cells (OSCs) by extending the exciton lifetime and diffusion distances, while the triplet non-fullerene acceptor materials have never been reported for bulk heterojunction OSCs. Herein, for the first time, three triplet molecular acceptors based on tellurophene with different degrees of ring fusing were designed and synthesized for OSCs. Significantly, these molecules have long exciton lifetime and diffusion lengths, leading to efficient power conversion efficiency (7.52 %), which is the highest value for tellurophene-based OSCs. The influence of the extent of ring fusing on molecular geometry and OSCs performance was investigated to show the power conversion efficiencies (PCEs) continuously increased along with increasing the extent of ring fusing. © 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Organic Donor-Acceptor Complexes as Novel Organic Semiconductors.

PubMed

Zhang, Jing; Xu, Wei; Sheng, Peng; Zhao, Guangyao; Zhu, Daoben

2017-07-18

Organic donor-acceptor (DA) complexes have attracted wide attention in recent decades, resulting in the rapid development of organic binary system electronics. The design and synthesis of organic DA complexes with a variety of component structures have mainly focused on metallicity (or even superconductivity), emission, or ferroelectricity studies. Further efforts have been made in high-performance electronic investigations. The chemical versatility of organic semiconductors provides DA complexes with a great number of possibilities for semiconducting applications. Organic DA complexes extend the semiconductor family and promote charge separation and transport in organic field-effect transistors (OFETs) and organic photovoltaics (OPVs). In OFETs, the organic complex serves as an active layer across extraordinary charge pathways, ensuring the efficient transport of induced charges. Although an increasing number of organic semiconductors have been reported to exhibit good p- or n-type properties (mobilities higher than 1 or even 10 cm 2 V -1 s -1 ), critical scientific challenges remain in utilizing the advantages of existing semiconductor materials for more and wider applications while maintaining less complicated synthetic or device fabrication processes. DA complex materials have revealed new insight: their unique molecular packing and structure-property relationships. The combination of donors and acceptors could offer practical advantages compared with their unimolecular materials. First, growing crystals of DA complexes with densely packed structures will reduce impurities and traps from the self-assembly process. Second, complexes based on the original structural components could form superior mixture stacking, which can facilitate charge transport depending on the driving force in the coassembly process. Third, the effective use of organic semiconductors can lead to tunable band structures, allowing the operation mode (p- or n-type) of the transistor to be

Growth of strain SES-3 with arsenate and other diverse electron acceptors

USGS Publications Warehouse

Laverman, A.M.; Blum, J.S.; Schaefer, J.K.; Phillips, E.J.P.; Lovley, D.R.; Oremland, R.S.

1995-01-01

The selenate-respiring bacterial strain SES-3 was able to use a variety of inorganic electron acceptors to sustain growth. SES-3 grew with the reduction of arsenate to arsenite, Fe(III) to Fe(II), or thiosulfate to sulfide. It also grew in medium in which elemental sulfur, Mn(IV), nitrite, trimethylamine N-oxide, or fumarate was provided as an electron acceptor. Growth on oxygen was microaerophilic. There was no growth with arsenite or chromate. Washed suspensions of cells grown on selenate or nitrate had a constitutive ability to reduce arsenate but were unable to reduce arsenite. These results suggest that strain SES-3 may occupy a niche as an environmental opportunist by being able to take advantage of a diversity of electron acceptors.

Effective Removal of Tetracycline from Aqueous Solution by Organic Acid-Coated Magnetic Nanoparticles.

PubMed

Guo, Liang; Liang, Yuyan; Chen, Xuelan; Xu, Wei; Wu, Kesheng; Wei, Hua; Xiong, Yonghua

2016-03-01

Self-assembled iron oxide nanocomposites are good magnetic nano-adsorbents that can be prepared using simple methods. Four types of organic acid-functionalised (oleic acid, undecenoic acid, caprylic acid or hexanoic acid) magnetic nanoparticles (MNPs) were synthesised through a one-pot chemisorption method for the removal of tetracycline (TC) from aqueous solution. The undecenoic acid-coated MNPs (UA-MNPs) exhibited the highest adsorption efficiency and can be easily retrieved with a low-gradient magnetic separator (0.4 Tesla) at pH 5.0 aqueous solution. The TC adsorption process on the UA-MNPs followed the Langmuir isotherm and the maximum adsorption capacities increased from 86.96 mg g(-1) to 222.2 mg g(-1) with the increase in temperature from 288 K to 318 K. The kinetics of adsorption fits pseudo-second-order model perfectly with a rate constant, 5.946 g mg(-1) min(-1) at 298 K. The positive values of the enthalpy (AH) and the negative value of the free energy (AG) indicated an endothermic and spontaneous adsorption process of TC on the UA-MNPs. Moreover, the UA-MNPs possessed excellent ability to adsorb the other three major types of TC antibiotics, including chlortetracycline, oxytetracycline and doxycycline.

A prospective randomized trial of two solutions for intrapartum amnioinfusion: effects on fetal electrolytes, osmolality, and acid-base status.

PubMed

Pressman, E K; Blakemore, K J

1996-10-01

Our purpose was to compare the effects of intrapartum amnioinfusion with normal saline solution versus lactated Ringer's solution plus physiologic glucose on neonatal electrolytes and acid-base balance. Patients undergoing amnioinfusion for obstetric indications were randomized to receive normal saline solution or lactated Ringer's solution plus physiologic glucose at standardized amnioinfusion rates. Data were collected prospectively on maternal demographics, course of labor, and maternal and neonatal outcome. Arterial cord blood was obtained for analysis of electrolytes, glucose, osmolality, lactic acid, and blood gases. Control subjects with normal fetal heart rate patterns, and clear amniotic fluid not receiving amnioinfusion were studied concurrently. Data were collected on 59 patients (21 normal saline solution, 18 lactated Ringer's solution plus physiologic glucose, and 20 controls). Maternal demographics, course of labor, and neonatal outcome were similar in all three groups. Cesarean sections were performed more often in the amnioinfusion groups (33.3% for normal saline solution, 38.9% for lactated Ringer's solution plus physiologic glucose) than in the control group (5.0%), p < 0.05. Cord arterial electrolytes, glucose, osmolality, lactic acid, and blood gases were not altered by amnioinfusion with either solution. Intrapartum amnioinfusion with normal saline solution or lactated Ringer's solution plus physiologic glucose has no effect on neonatal electrolytes or acid-base balance.

Diphenylphenoxy-Thiophene-PDI Dimers as Acceptors for OPV Applications with Open Circuit Voltage Approaching 1 Volt.

PubMed

Stenta, Caterina; Molina, Desiré; Viterisi, Aurélien; Montero-Rama, María Pilar; Pla, Sara; Cambarau, Werther; Fernández-Lázaro, Fernando; Palomares, Emilio; Marsal, Lluis F; Sastre-Santos, Ángela

2018-03-30

Two new perylenediimides (PDIs) have been developed for use as electron acceptors in solution-processed bulk heterojunction solar cells. The compounds were designed to exhibit maximal solubility in organic solvents, and reduced aggregation in the solid state. In order to achieve this, diphenylphenoxy groups were used to functionalize a monomeric PDI core, and two PDI dimers were bridged with either one or two thiophene units. In photovoltaic devices prepared using PDI dimers and a monomer in conjunction with PTB7, it was found that the formation of crystalline domains in either the acceptor or donor was completely suppressed. Atomic force microscopy, X-ray diffraction, charge carrier mobility measurements and recombination kinetics studies all suggest that the lack of crystallinity in the active layer induces a significant drop in electron mobility. Significant surface recombination losses associated with a lack of segregation in the material were also identified as a significant loss mechanism. Finally, the monomeric PDI was found to have sub-optimum LUMO energy matching the cathode contact, thus limiting charge carrier extraction. Despite these setbacks, all PDIs produced high open circuit voltages, reaching almost 1 V in one particular case.

Molecular origin of photovoltaic performance in donor- block-acceptor all-conjugated block copolymers

DOE PAGES

Smith, Kendall A.; Lin, Yen -Hao; Mok, Jorge W.; ...

2015-11-03

All-conjugated block copolymers may be an effective route to self-assembled photovoltaic devices, but we lack basic information on the relationship between molecular characteristics and photovoltaic performance. Here, we synthesize a library of poly(3-hexylthiophene) (P3HT) block poly((9,9-dialkylfluorene)-2,7-diyl-alt-[4,7-bis(alkylthiophen-5-yl)-2,1,3-benzothiadiazole]-2',2''-diyl) (PFTBT) donor- block-acceptor all-conjugated block copolymers and carry out a comprehensive study of processing conditions, crystallinity, domain sizes, and side-chain structure on photovoltaic device performance. We find that all block copolymers studied exhibit an out-of-plane crystal orientation after deposition, and on thermal annealing at high temperatures the crystal orientation flips to an in-plane orientation. By varying processing conditions on polymer photovoltaic devices, we showmore » that the crystal orientation has only a modest effect (15-20%) on photovoltaic performance. The addition of side-chains to the PFTBT block is found to decrease photovoltaic power conversion efficiencies by at least an order of magnitude. Through grazing-incidence X-ray measurements we find that the addition of side-chains to the PFTBT acceptor block results in weak segregation and small (< 10 nm) block copolymer self-assembled donor and acceptor domains. This work is the most comprehensive to date on all-conjugated block copolymer systems and suggests that photovoltaic performance of block copolymers depends strongly on the miscibility of donor and acceptor blocks, which impacts donor and acceptor domain sizes and purity. Lastly, strategies for improving the device performance of block copolymer photovoltaics should seek to increase segregation between donor and acceptor polymer domains.« less

Molecular origin of photovoltaic performance in donor- block-acceptor all-conjugated block copolymers

DOE Office of Scientific and Technical Information (OSTI.GOV)

Smith, Kendall A.; Lin, Yen -Hao; Mok, Jorge W.

All-conjugated block copolymers may be an effective route to self-assembled photovoltaic devices, but we lack basic information on the relationship between molecular characteristics and photovoltaic performance. Here, we synthesize a library of poly(3-hexylthiophene) (P3HT) block poly((9,9-dialkylfluorene)-2,7-diyl-alt-[4,7-bis(alkylthiophen-5-yl)-2,1,3-benzothiadiazole]-2',2''-diyl) (PFTBT) donor- block-acceptor all-conjugated block copolymers and carry out a comprehensive study of processing conditions, crystallinity, domain sizes, and side-chain structure on photovoltaic device performance. We find that all block copolymers studied exhibit an out-of-plane crystal orientation after deposition, and on thermal annealing at high temperatures the crystal orientation flips to an in-plane orientation. By varying processing conditions on polymer photovoltaic devices, we showmore » that the crystal orientation has only a modest effect (15-20%) on photovoltaic performance. The addition of side-chains to the PFTBT block is found to decrease photovoltaic power conversion efficiencies by at least an order of magnitude. Through grazing-incidence X-ray measurements we find that the addition of side-chains to the PFTBT acceptor block results in weak segregation and small (< 10 nm) block copolymer self-assembled donor and acceptor domains. This work is the most comprehensive to date on all-conjugated block copolymer systems and suggests that photovoltaic performance of block copolymers depends strongly on the miscibility of donor and acceptor blocks, which impacts donor and acceptor domain sizes and purity. Lastly, strategies for improving the device performance of block copolymer photovoltaics should seek to increase segregation between donor and acceptor polymer domains.« less

Energy transfer and correlations in cavity-embedded donor-acceptor configurations.

PubMed

Reitz, Michael; Mineo, Francesca; Genes, Claudiu

2018-06-13

The rate of energy transfer in donor-acceptor systems can be manipulated via the common interaction with the confined electromagnetic modes of a micro-cavity. We analyze the competition between the near-field short range dipole-dipole energy exchange processes and the cavity mediated long-range interactions in a simplified model consisting of effective two-level quantum emitters that could be relevant for molecules in experiments under cryogenic conditions. We find that free-space collective incoherent interactions, typically associated with sub- and superradiance, can modify the traditional resonant energy transfer scaling with distance. The same holds true for cavity-mediated collective incoherent interactions in a weak-coupling but strong-cooperativity regime. In the strong coupling regime, we elucidate the effect of pumping into cavity polaritons and analytically identify an optimal energy flow regime characterized by equal donor/acceptor Hopfield coefficients in the middle polariton. Finally we quantify the build-up of quantum correlations in the donor-acceptor system via the two-qubit concurrence as a measure of entanglement.

Vacancy clustering and acceptor activation in nitrogen-implanted ZnO

NASA Astrophysics Data System (ADS)

Børseth, Thomas Moe; Tuomisto, Filip; Christensen, Jens S.; Monakhov, Edouard V.; Svensson, Bengt G.; Kuznetsov, Andrej Yu.

2008-01-01

The role of vacancy clustering and acceptor activation on resistivity evolution in N ion-implanted n -type hydrothermally grown bulk ZnO has been investigated by positron annihilation spectroscopy, resistivity measurements, and chemical profiling. Room temperature 220keV N implantation using doses in the low 1015cm-2 range induces small and big vacancy clusters containing at least 2 and 3-4 Zn vacancies, respectively. The small clusters are present already in as-implanted samples and remain stable up to 1000°C with no significant effect on the resistivity evolution. In contrast, formation of the big clusters at 600°C is associated with a significant increase in the free electron concentration attributed to gettering of amphoteric Li impurities by these clusters. Further annealing at 800°C results in a dramatic decrease in the free electron concentration correlated with activation of 1016-1017cm-3 acceptors likely to be N and/or Li related. The samples remain n type, however, and further annealing at 1000°C results in passivation of the acceptor states while the big clusters dissociate.

Incorporating fluorinated moieties in fully conjugated donor-acceptor block copolymers

NASA Astrophysics Data System (ADS)

Lee, Youngmin; Wang, Qing; Gomez, Enrique D.

Fully conjugated donor-acceptor block copolymers are promising candidates for photovoltaics due to their ability to microphase separate at length scales commensurate with exciton diffusion lengths. These materials can also serve as model systems to study the relationship between molecular structure, microstructure, and optoelectronic properties of conjugated polymers. The development of new donor-acceptor block copolymers relies on the manipulation of the chemical structure to fine tune properties and improve overall performance when employed in photovoltaic devices. To this end, we have demonstrated the incorporation of fluorinated moieties in conjugated block copolymers. The introduction of fluorine, a strong electron withdrawing element, is known to influence phase separation and the bandgap, and as a result, optoelectronic properties. Fluorine was introduced to the acceptor block of poly(3-hexylthiophene-2,5-diyl)-block-poly((9,9-bis(2-octyl)fluorene-2,7-diyl)-alt-(4,7-di(thiophene-2-yl)-2,1,3-benzothiadiazole)-5 ',5?-diyl) (P3HT- b-PFTBT). PFTBTs were prepared with di-fluorinated and mono-fluorinated TBT. We find that fluorination impacts the bandgap, morphology and performance in devices.

Influence of the local environment on Mn acceptors in GaAs

NASA Astrophysics Data System (ADS)

Lee, Donghun; Gohlke, David; Benjamin, Anne; Gupta, Jay A.

2015-04-01

As transistors continue to shrink toward nanoscale dimensions, their characteristics are increasingly dependent on the statistical variations of impurities in the semiconductor material. The scanning tunneling microscope (STM) can be used to not only study prototype devices with atomically precise placement of impurity atoms, but can also probe how the properties of these impurities depend on the local environment. Tunneling spectroscopy of Mn acceptors in GaAs indicates that surface-layer Mn act as a deep acceptor, with a hole binding energy that can be tuned by positioning charged defects nearby. Band bending induced by the tip or by these defects can also tune the ionization state of the acceptor complex, evident as a ring-like contrast in STM images. The interplay of these effects is explored over a wide range of defect distances, and understood using iterative simulations of tip-induced band bending.

Adsorption of Cu(II) from aqueous solution on sulfuric acid treated palygorskite

NASA Astrophysics Data System (ADS)

Niu, Yan-Ning; Yuan, Yuan; Gao, Wei-Xin; Qian, Sheng; Sun, Wen

2018-03-01

The absorption behavior of Cu2+ from aqueous solution on sulfuric acid treated palygorskite were investigated, the results showed that palygorskite had high absorption ability for Cu2+ from aqueous solution. Effects of the shaking time, pH and the copper ion concentration on the removal rate were discussed. The absorption behavior of Cu2+ could be well imitated by the Langmuir isothermal equation.

Competitive adsorption of boric acid and chromate onto alumina in aqueous solutions.

PubMed

Demetriou, A; Pashalidis, I

2014-01-01

The competitive adsorption of boric acid and chromate from aqueous solutions by alumina has been investigated by spectrophotometry at pH 8, ionic strength = 0.0, 0.1 and 1.0 M NaClO4, T = 22 ± 3 °C and under normal atmospheric conditions. The experimental data show that addition of excess boric acid in the system leads to the increase of Cr(VI) concentration in solution, indicating the replacement of adsorbed chromate by boron on the alumina surface. Data evaluation results in the determination of the competition reaction constant and the formation constant of the Cr(VI) surface complexes, which are logKCr(VI)-B(III) = -3.5 ± 0.2 and logβ*Cr = 7.6 ± 0.3, respectively.

A novel method for determination and quantification of 4-methyloctanoic and 4-methylnonanoic acids in mutton by hollow fiber supported liquid membrane extraction coupled with gas chromatography.

PubMed

Chen, Haigui; Wang, Yunfan; Jiang, Houyang; Zhao, Guohua

2012-12-01

4-Methyloctanoic acid (MOA) and 4-methylnonanoic acid (MNA) are the main compounds responsible for "sweaty" odor of mutton. A novel method for their determination has been developed and validated. Hollow fiber supported liquid membrane (HF-SLM) was applied to selectively extract MOA and MNA prior to gas chromatography (GC) analysis. For HF-SLM, the donor outside the fiber was the acidified supernatant (pH 4) from aqueous mutton slurry. Liquid membrane was 5% tri-n-octylphoshphine oxide in di-n-hexyl ether and 0.3M NaOH aqueous solution filled in the lumen of the fiber was used as the acceptor. The extraction last for 4h. After acidification with HCl, the acceptor was directly analyzed by GC. Importantly, HF-SLM provided high enrichment factors for MOA (133) and MNA (116). The method developed had low detection limits of 0.0007-0.0015 mg/kg, good linearity (R²>0.9956), reasonable recovery (88.54-122.13%), satisfactory intra-assay (7.83-9.73%) and inter-assay (15.68-16.14%) precision. Copyright © 2012 Elsevier Ltd. All rights reserved.

A fused-ring acceptor unit in d-a copolymers benefits photovoltaic performance.

PubMed

Zuo, Chuantian; Cao, Jiamin; Ding, Liming

2014-08-01

Pentacyclic lactam acceptor unit TPTI invented by our group is proved to be a good building block for efficient D-A copolymers used in organic solar cells. Here, two D-A copolymers PBTTPTI and PTTTPTI are developed by copolymerizing TPTI with 2,2'-bithiophene (BT) or thieno[3,2-b]thiophene (TT). PBTTPTI and PTTTPTI exhibit good solubility and strong interchain π-π interaction even in dilute solution. They possess deep HOMO levels (ca. -5.3 eV), partial crystallinity, and good hole mobilities. Blending with PC71 BM, PBTTPTI and PTTTPTI give decent power conversion efficiencies (PCE) up to 6.83% and 5.86%, with outstanding fill factors (FF) of 74.3% and 71.3%, respectively. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Fundamental Studies on Donor-acceptor Conjugated Polymers Containing 'Heavy' Group 14 and Group 16 Elements

NASA Astrophysics Data System (ADS)

Gibson, Gregory Laird

One advantage of conjugated polymers as organic materials is that their properties may be readily tuned through covalent modifications. This thesis presents studies on the structure-property relationships resulting from single- and double-atom substitutions on an alternating donor-acceptor conjugated polymer. Specifically, single selenium and tellurium atoms have been incorporated into the acceptor monomer in place of sulfur; silicon and germanium atoms have been substituted in place of carbon at the donor monomer bridge position. The carbon-donor/ tellurium-acceptor polymer was synthesized by a post-polymerization reaction sequence and demonstrated the utility of heavy group 16 atoms to red shift a polymer absorption spectrum. Density functional theory calculations point to a new explanation for this result invoking the lower heavy atom ionization energy and reduced aromaticity of acceptor monomers containing selenium and tellurium compared to sulfur. Absorption and emission experiments demonstrate that both silicon and germanium substitutions in the donor slightly blue shift the polymer absorption spectrum. Polymers containing sulfur in the acceptor are the strongest light absorbers of all polymers studied here. Molecular weight and phenyl end capping studies show that molecular weight appears to affect polymer absorption to the greatest degree in a medium molecular weight regime and that these effects have a significant aggregation component. Solar cell devices containing either the silicon- or germanium-donor/selenium-acceptor polymer display improved red light harvesting or hole mobility relative to their structural analogues. Overall, these results clarify the effects of single atom substitution on donor-acceptor polymers and aid in the future design of polymers containing heavy atoms.

Acid-Base Properties of Azo Dyes in Solution Studied Using Spectrophotometry and Colorimetry

NASA Astrophysics Data System (ADS)

Snigur, D. V.; Chebotarev, A. N.; Bevziuk, K. V.

2018-03-01

Colorimetry and spectrophotometry with chemometric data processing were used to study the acid-base properties of azo dyes in aqueous solution. The capabilities of both methods were compared. Ionization constants of all the functional groups of the azo compounds studied could be determined relative to the change in the specific color difference depending on the acidity of the medium. The colorimetric functions of ion-molecular forms of azo compounds used as an analytical signal allow us to obtain complete information on the acid-base equilibrium in a wide acidity range.

Internal structure of acceptor-bound excitons in wide-band-gap wurtzite semiconductors

NASA Astrophysics Data System (ADS)

Gil, Bernard; Bigenwald, Pierre; Paskov, Plamen P.; Monemar, Bo

2010-02-01

We describe the internal structure of acceptor-bound excitons in wurtzite semiconductors. Our approach consists in first constructing, in the context of angular momentum algebra, the wave functions of the two-hole system that fulfill Pauli’s exclusion’s principle. Second, we construct the acceptor-bound exciton states by adding the electron states in a similar manner that two-hole states are constructed. We discuss the optical selection rules for the acceptor-bound exciton recombination. Finally, we compare our theory with experimental data for CdS and GaN. In the specific case of CdS for which much experimental information is available, we demonstrate that, compared with cubic semiconductors, the sign of the short-range hole-exchange interaction is reversed and more than one order of magnitude larger. The whole set of data is interpreted in the context of a large value of the short-range hole-exchange interaction Ξ0=3.4±0.2meV . This value dictates the splitting between the ground-state line I1 and the other transitions. The values we find for the electron-hole spin-exchange interaction and of the crystal-field splitting of the two-hole state are, respectively, -0.4±0.1 and 0.2±0.1meV . In the case of GaN, the experimental data for the acceptor-bound excitons in the case of Mg and Zn acceptors, show more than one bound-exciton line. We discuss a possible assignment of these states.

Effect of Boric Acid Versus Conventional Irrigation Solutions on the Bond Strength Between Fiber Post 
and Root Dentin.

PubMed

Culhaoglu, Ahmet Kursad; Özcan, Erdal; Kilicarslan, Mehmet Ali; Seker, Emre

2017-01-01

To compare the effect of boric acid solutions of different percentages to conventional irrigation solutions on the adhesive bond strength between fiber posts and radicular dentin surface with different cement types. One hundred fifteen extracted human incisors were endodontically instrumented to a length of 14-15 mm, and 12-mm post spaces were prepared with specific drills. Cylindrical fiber posts (Panavia Post) were luted with two different composite cements (Panavia F 2.0, Panavia SA) and cut into 1-mm-thick slices. These specimens were randomly allocated to 5 groups according to the irrigant applied: 1. control, no irrigant; 2. 10 ml of 2% chlorhexidine; 3. 10 ml of 5.25% NaOCl for 5 min and 10 ml of 17% EDTA for 3 min; 4. 10 ml of 5% boric acid solution at a temperature of 55°C for 60 s; 5. 10% boric acid solution, conditions as in group 4. Bond strength was determined using the push-out test. Microscopic assessment and SEM evaluations were performed in combination with push-out tests. The push-out bond strengths of cervical segments were significantly higher than for the middle and apical segments in all groups. The type of irrigation solution used significantly affected the bond strengths of the posts. The 10% boric acid solution and EDTA + NaOCl irrigation solutions provided the highest bond strengths (p < 0.005). SEM analysis showed that the dentin tubules were open and the smear layer was completely removed when EDTA/NaOCl and 10% boric acid were used as irrigation agents. Boric acid solutions, especially at a concentration of 10%, can be a viable alternative to the conventional irrigants used during endodontic treatment. The extent to which the 10% boric acid solution successfully removed the smear layer and the ease of rinsing boric acid from the root surface are advantageous.

Large-scale production of anhydrous nitric acid and nitric acid solutions of dinitrogen pentoxide

DOEpatents

Harrar, Jackson E.; Quong, Roland; Rigdon, Lester P.; McGuire, Raymond R.

2001-01-01

A method and apparatus are disclosed for a large scale, electrochemical production of anhydrous nitric acid and N.sub.2 O.sub.5. The method includes oxidizing a solution of N.sub.2 O.sub.4 /aqueous-HNO.sub.3 at the anode, while reducing aqueous HNO.sub.3 at the cathode, in a flow electrolyzer constructed of special materials. N.sub.2 O.sub.4 is produced at the cathode and may be separated and recycled as a feedstock for use in the anolyte. The process is controlled by regulating the electrolysis current until the desired products are obtained. The chemical compositions of the anolyte and catholyte are monitored by measurement of the solution density and the concentrations of N.sub.2 O.sub.4.

Solubility Limits of Dibutyl Phosphoric Acid in Uranium Solutions at SRS

DOE Office of Scientific and Technical Information (OSTI.GOV)

Thompson, M.C.; Pierce, R.A.; Ray, R.J.

1998-06-01

The Savannah River Site has enriched uranium (EU) solution which has been stored for almost 10 years since being purified in the second uranium cycle of the H area solvent extraction process. The concentrations in solution are {tilde 6} g/L U and about 0.1 M nitric acid. Residual tributylphosphate in the solutions has slowly hydrolyzed to form dibutyl phosphoric acid (HDBP) at concentrations averaging 50 mg/L. Uranium is known to form compounds with DBP which have limited solubility. The potential to form uranium-DBP solids raises a nuclear criticality safety issue. SRTC tests have shown that U-DBP solids will precipitate atmore » concentrations potentially attainable during storage of enriched uranium solutions. Evaporation of the existing EUS solution without additional acidification could result in the precipitation of U-DBP solids if DBP concentration in the resulting solution exceeds 110 ppm at ambient temperature. The same potential exists for evaporation of unwashed 1CU solutions. The most important variables of interest for present plant operations are HNO{sub 3} and DBP concentrations. Temperature is also an important variable controlling precipitation. The data obtained in these tests can be used to set operating and safety limits for the plant. It is recommended that the data for 0 degrees C with 0.5 M HNO{sub 3} be used for setting the limits. The limit would be 80 mg/L which is 3 standard deviations below the average of 86 observed in the tests. The data shows that super-saturation can occur when the DBP concentration is as much as 50 percent above the solubility limit. However, super-saturation cannot be relied on for maintaining nuclear criticality safety. The analytical method for determining DBP concentration in U solutions was improved so that analyses for a solution are accurate to within 10 percent. However, the overall uncertainty of results for periodic samples of the existing EUS solutions was only reduced slightly. Thus, sampling appears

Effect of adding acid solution on setting time and compressive strength of high calcium fly ash based geopolymer

NASA Astrophysics Data System (ADS)

Antoni, Herianto, Jason Ghorman; Anastasia, Evelin; Hardjito, Djwantoro

2017-09-01

Fly ash with high calcium oxide content when used as the base material in geopolymer concrete could cause flash setting or rapid hardening. However, it might increase the compressive strength of geopolymer concrete. This rapid hardening could cause problems if the geopolymer concrete is used on a large scale casting that requires a long setting time. CaO content can be indicated by pH values of the fly ash, while higher pH is correlated with the rapid setting time of fly ash-based geopolymer. This study investigates the addition of acid solution to reduce the initial pH of the fly ash and to prolong the setting time of the mixture. The acids used in this study are hydrochloric acid (HCl), sulfuric acid (H2 SO4), nitric acid (HNO3) and acetic acid (CH3 COOH). It was found that the addition of acid solution in fly ash was able to decrease the initial pH of fly ash, however, the initial setting time of geopolymer was not reduced. It was even faster than that of the control mixture. The acid type causes various influence, depending on the fly ash properties. In addition, the use of acid solution in fly ash reduces the compressive strength of geopolymer mortar. It is concluded that the addition of acid solution cannot prolong the rapid hardening of high calcium fly ash geopolymer, and it causes adverse effect on the compressive strength.

Effects Sprayed Solution of Salicylic Acid to Prevent of Wilt Disease Caused by Fussarium oxysporium

NASA Astrophysics Data System (ADS)

Yousif, Dina. Y. M.

2018-05-01

The current search aimed to detective the effect of sprayed solution of salicylic acid on plant and leaves of sweet green pepper (Capsicum annuum) for control the pathogen Fussarium oxysporium compering with control plant and leaves. Results indicated that, the spray of salicylic acid at concentration 0.5 g/L is effecting the fungal infection through prevent transport fungus F. oxysporum to the neighboring green pepper plant. The number of dead green pepper plant after sprayed with solution of salicylic acid and only water they were (4, 6, and 3) (8, 9, and 10) respectively. While the experimental infection of green pepper leaves after inoculated the fungus as local spot by scorching small spots of these leaves with the aid of hot nail. These spots were then exposed to the 0.5 g/L aqueous solution salicylic acid before and after the inoculation of the fungus. The spray of salicylic acid before 24 and 48 hour prevent the development of disease and make a good protection of the mention leaves from infection with this fungus, the diameter of leaves lesion (1,1.5 cm) respectively. while the ability of fungus to grow after 24 and 48 hour from salicylic acid treatment was markedly reduce as compared with control, such treatment show slow growth of pathogen infect.

Effect of molecular structure of aniline-formaldehyde copolymers on corrosion inhibition of mild steel in hydrochloric acid solution.

PubMed

Zhang, Yan; Nie, Mengyan; Wang, Xiutong; Zhu, Yukun; Shi, Fuhua; Yu, Jianqiang; Hou, Baorong

2015-05-30

Aniline-formaldehyde copolymers with different molecular structures have been prepared and investigated for the purpose of corrosion control of mild steel in hydrochloric acid. The copolymers were synthesized by a condensation polymerization process with different ratios of aniline to formaldehyde in acidic precursor solutions. The corrosion inhibition efficiency of as-synthesized copolymers for Q235 mild steel was investigated in 1.0 mol L(-1) hydrochloric acid solution by weight loss measurement, potentiodynamic polarization, and electrochemical impedance spectroscopy, respectively. All the results demonstrate that as-prepared aniline-formaldehyde copolymers are efficient mixed-type corrosion inhibitors for mild steels in hydrochloric acid. The corrosion inhibition mechanism is discussed in terms of the role of molecular structure on adsorption of the copolymers onto the steel surface in acid solution. Copyright © 2015. Published by Elsevier B.V.

[Analyze nanofiltration separation rule of chlorogenic acid from low concentration ethanol by Donnan effect and solution-diffusion effect].

PubMed

Li, Cun-Yu; Liu, Li-Cheng; Jin, Li-Yang; Li, Hong-Yang; Peng, Guo-Ping

2017-07-01

To separate chlorogenic acid from low concentration ethanol and explore the influence of Donnan effect and solution-diffusion effect on the nanofiltration separation rule. The experiment showed that solution pH and ethanol volume percent had influences on the separation of chlorogenic acid. Within the pH values from 3 to 7 for chlorogenic acid in 30% ethanol, the rejection rate of chlorogenic acid was changed by 70.27%. Through the response surface method for quadratic regression model, an interaction had been found in molecule weight cut-off, pH and ethanol volume percent. In fixed nanofiltration apparatus, the existence states of chlorogenic acid determinedits separation rules. With the increase of ethanol concentration, the free form chlorogenic acid was easily adsorbed, dissolved on membrane surface and then caused high transmittance due to the solution-diffusion effect. However, at the same time, due to the double effects of Donnan effect and solution-diffusion effect, the ionic state of chlorogenic acid was hard to be adsorbed in membrane surface and thus caused high rejection rate. The combination of Box-Behnken design and response surface analysis can well optimize the concentrate process by nanofiltration, and the results showed that nanofiltration had several big advantages over the traditional vacuum concentrate technology, meanwhile, and solved the problems of low efficiency and serious component lossesin the Chinese medicines separation process for low concentration organic solvent-water solution. Copyright© by the Chinese Pharmaceutical Association.

Part I. Synthesis and Characterization of Donor-Pi-Acceptor Compounds with Pentadienyl-Bridged Indoline and Tetrahydroquinoline Donors and Aldehyde and Thiobarbituric Acid Acceptors Part II. Longitudinal Study Comparing Online versus Face-to-Face Course Delivery in Introductory Chemistry

ERIC Educational Resources Information Center

Greco, Patrick F.

2012-01-01

Part I. The design and development of organic second-order nonlinear optical (NLO) materials have attracted much interest due to their applications in optoelectronic devices and modern communications technology. Donor-pi-acceptor compounds, D-(CH=CH)[subscript n]-A, often exhibit hyperpolarizability that results in laser frequency doubling (second…

The Effect of Acceptor and Donor Doping on Oxygen Vacancy Concentrations in Lead Zirconate Titanate (PZT).

PubMed

Slouka, Christoph; Kainz, Theresa; Navickas, Edvinas; Walch, Gregor; Hutter, Herbert; Reichmann, Klaus; Fleig, Jürgen

2016-11-22

The different properties of acceptor-doped (hard) and donor-doped (soft) lead zirconate titanate (PZT) ceramics are often attributed to different amounts of oxygen vacancies introduced by the dopant. Acceptor doping is believed to cause high oxygen vacancy concentrations, while donors are expected to strongly suppress their amount. In this study, La 3+ donor-doped, Fe 3+ acceptor-doped and La 3+ /Fe 3+ -co-doped PZT samples were investigated by oxygen tracer exchange and electrochemical impedance spectroscopy in order to analyse the effect of doping on oxygen vacancy concentrations. Relative changes in the tracer diffusion coefficients for different doping and quantitative relations between defect concentrations allowed estimates of oxygen vacancy concentrations. Donor doping does not completely suppress the formation of oxygen vacancies; rather, it concentrates them in the grain boundary region. Acceptor doping enhances the amount of oxygen vacancies but estimates suggest that bulk concentrations are still in the ppm range, even for 1% acceptor doping. Trapped holes might thus considerably contribute to the charge balancing of the acceptor dopants. This could also be of relevance in understanding the properties of hard and soft PZT.

The Effect of Acceptor and Donor Doping on Oxygen Vacancy Concentrations in Lead Zirconate Titanate (PZT)

PubMed Central

Slouka, Christoph; Kainz, Theresa; Navickas, Edvinas; Walch, Gregor; Hutter, Herbert; Reichmann, Klaus; Fleig, Jürgen

2016-01-01

The different properties of acceptor-doped (hard) and donor-doped (soft) lead zirconate titanate (PZT) ceramics are often attributed to different amounts of oxygen vacancies introduced by the dopant. Acceptor doping is believed to cause high oxygen vacancy concentrations, while donors are expected to strongly suppress their amount. In this study, La3+ donor-doped, Fe3+ acceptor-doped and La3+/Fe3+-co-doped PZT samples were investigated by oxygen tracer exchange and electrochemical impedance spectroscopy in order to analyse the effect of doping on oxygen vacancy concentrations. Relative changes in the tracer diffusion coefficients for different doping and quantitative relations between defect concentrations allowed estimates of oxygen vacancy concentrations. Donor doping does not completely suppress the formation of oxygen vacancies; rather, it concentrates them in the grain boundary region. Acceptor doping enhances the amount of oxygen vacancies but estimates suggest that bulk concentrations are still in the ppm range, even for 1% acceptor doping. Trapped holes might thus considerably contribute to the charge balancing of the acceptor dopants. This could also be of relevance in understanding the properties of hard and soft PZT. PMID:28774067

PHYSICAL SOLUTIONS FOR ACID ROCK DRAINAGE AT REMOTE SITES DEMONSTRATION PROJECT

EPA Science Inventory

This report summarizes the results of Mine Waste Technology Program, Activity III, Project 42, Physical Solutions for Acid Rock Drainage at Remote Sites, funded by the U.S. Environmental Protection Agency (EPA) and jointly administered by EPA and the U.S. Department of Energy. A...

Resonance Energy Transfer-Based Nucleic Acid Hybridization Assays on Paper-Based Platforms Using Emissive Nanoparticles as Donors.

PubMed

Doughan, Samer; Noor, M Omair; Han, Yi; Krull, Ulrich J

2017-01-01

Quantum dots (QDs) and upconverting nanoparticles (UCNPs) are luminescent nanoparticles (NPs) commonly used in bioassays and biosensors as resonance energy transfer (RET) donors. The narrow and tunable emissions of both QDs and UCNPs make them versatile RET donors that can be paired with a wide range of acceptors. Ratiometric signal processing that compares donor and acceptor emission in RET-based transduction offers improved precision, as it accounts for fluctuations in the absolute photoluminescence (PL) intensities of the donor and acceptor that can result from experimental and instrumental variations. Immobilizing NPs on a solid support avoids problems such as those that can arise with their aggregation in solution, and allows for facile layer-by-layer assembly of the interfacial chemistry. Paper is an attractive solid support for the development of point-of-care diagnostic assays given its ubiquity, low-cost, and intrinsic fluid transport by capillary action. Integration of nanomaterials with paper-based analytical devices (PADs) provides avenues to augment the analytical performance of PADs, given the unique optoelectronic properties of nanomaterials. Herein, we describe methodology for the development of PADs using QDs and UCNPs as RET donors for optical transduction of nucleic acid hybridization. Immobilization of green-emitting QDs (gQDs) on imidazole functionalized cellulose paper is described for use as RET donors with Cy3 molecular dye as acceptors for the detection of SMN1 gene fragment. We also describe the covalent immobilization of blue-emitting UCNPs on aldehyde modified cellulose paper for use as RET donors with orange-emitting QDs (oQDs) as acceptors for the detection of HPRT1 gene fragment. The data described herein is acquired using an epifluorescence microscope, and can also be collected using technology such as a typical electronic camera.

Electron paramagnetic resonance study of neutral Mg acceptors in β-Ga2O3 crystals

NASA Astrophysics Data System (ADS)

Kananen, B. E.; Halliburton, L. E.; Scherrer, E. M.; Stevens, K. T.; Foundos, G. K.; Chang, K. B.; Giles, N. C.

2017-08-01

Electron paramagnetic resonance (EPR) is used to directly observe and characterize neutral Mg acceptors ( M gGa0 ) in a β-Ga2O3 crystal. These acceptors, best considered as small polarons, are produced when the Mg-doped crystal is irradiated at or near 77 K with x rays. During the irradiation, neutral acceptors are formed when holes are trapped at singly ionized Mg acceptors ( M gGa- ). Unintentionally present Fe3+ (3d5) and Cr3+ (3d3) transition-metal ions serve as the corresponding electron traps. The hole is localized in a nonbonding p orbital on a threefold-coordinated oxygen ion adjacent to an Mg ion at a sixfold-coordinated Ga site. These M gGa0 acceptors (S = 1/2) have a slightly anisotropic g matrix (principal values are 2.0038, 2.0153, and 2.0371). There is also partially resolved 69Ga and 71Ga hyperfine structure resulting from unequal interactions with the two Ga ions adjacent to the hole. With the magnetic field along the a direction, hyperfine parameters are 2.61 and 1.18 mT for the 69Ga nuclei at the two inequivalent neighboring Ga sites. The M gGa0 acceptors thermally convert back to their nonparamagnetic M gGa- charge state when the temperature of the crystal is raised above approximately 250 K.

Benzimidazole acrylonitriles as multifunctional push-pull chromophores: Spectral characterisation, protonation equilibria and nanoaggregation in aqueous solutions

NASA Astrophysics Data System (ADS)

Horak, Ema; Vianello, Robert; Hranjec, Marijana; Krištafor, Svjetlana; Zamola, Grace Karminski; Steinberg, Ivana Murković

2017-05-01

Heterocyclic donor-π-acceptor molecular systems based on an N,N-dimethylamino phenylacrylonitrile benzimidazole skeleton have been characterised and are proposed for potential use in sensing applications. The benzimidazole moiety introduces a broad spectrum of useful multifunctional properties to the system including electron accepting ability, pH sensitivity and compatibility with biomolecules. The photophysical characterisation of the prototropic forms of these chromophores has been carried out in both solution and on immobilisation in polymer films. The experimental results are further supported by computational determination of pKa values. It is noticed that compound 3 forms nanoaggregates in aqueous solutions with aggregation-induced emission (AIE) at 600 nm. All the systems demonstrate spectral pH sensitivity in acidic media which shifts towards near-neutral values upon immobilisation in polymer films or upon aggregation in an aqueous environment (compound 3). The structure-property relationships of these functional chromophores, involving their spectral characteristics, acid-base equilibria, pKa values and aggregation effects have been determined. Potential applications of the molecules as pH and biomolecular sensors are proposed based on their pH sensitivity and AIE properties.

Adsorption of Copper Ion using Acrylic Acid-g-Polyaniline in Aqueous Solution

NASA Astrophysics Data System (ADS)

Kamarudin, Sabariah; Mohammad, Masita

2018-04-01

A conductive polymer, polyaniline (PANI) has unique electrical behaviour, stable in the environment, easy synthesis and have wide application in various fields. Modification of PANI in order to improve its adsorption capacity has been done. In this study, the polyaniline-grafted acrylic acid has been prepared and followed by adsorption of copper ion in aqueous solution. Acrylic acid, PANI and acrylic acid-g-polyaniline (Aag-PANI) were characterized by FTIR and SEM to determine its characteristic. The adsorption capacity was investigated to study the removal capacity of Cu ion from aqueous solution. Two parameters were selected which are pH (2, 4 and 6) and initial metal ion concentration (50 mg/L, 100 mg/L and 200 mg/L). The maximum adsorption capacity for PANI and Aag-PANI are 1.7 mg/g and 64.6 mg/g, respectively, at an initial concentration of 100 mg/L. The Langmuir adsorption isotherm model and Freundlich adsorption isotherm model have been used and showed that it is heterolayer adsorption by follows the Freundlich isotherm model.

Conformation of kainic acid in solution from molecular modelling and NMR spectra.

PubMed

Falk, M; Sidhu, P; Walter, J A

1998-01-01

Conformational behaviour of kainic acid in aqueous solution was elucidated by molecular mechanics and dynamics. The pucker of the five-membered ring in kainic acid was examined and compared with that of model compounds. In cyclopentane there is no barrier to pseudorotation, so that all puckered states coexist. In pyrrolidinium, the presence of a hetero-atom in the ring introduces a small barrier (about 0.6 kcal mol(-1)) to pseudorotation, separating two stable regions, A and B, which are equivalent by symmetry. In proline, the presence of the carboxylate group on C2 removes the symmetry but two stable conformational minima, A and B, remain. In kainic acid, the presence of side-chains on C3 and C4 introduces complications resulting in additional sub-minima in both regions, A and B. In solution, kainic acid is a complex mixture of conformers with comparable energies, because of the combination of several stable states of the pyrrolidinium ring with the torsional degrees of freedom arising from the two side-chains. The individual geometries, energies, and estimates of relative populations of these conformers were obtained from molecular dynamics simulations. The calculations were validated by a comparison of predicted inter-proton distances and vicinal proton coupling constants with the experimental quantities derived from NMR spectra.

A systematic analysis of acceptor specificity and reaction kinetics of five human α(2,3)sialyltransferases: Product inhibition studies illustrate reaction mechanism for ST3Gal-I

DOE Office of Scientific and Technical Information (OSTI.GOV)

Gupta, Rohitesh, E-mail: rohitesh.gupta@gmail.com; Matta, Khushi L.; Neelamegham, Sriram, E-mail: neel@buffalo.edu

2016-01-15

Sialyltransferases (STs) catalyze the addition of sialic acids to the non-reducing ends of glycoproteins and glycolipids. In this work, we examined the acceptor specificity of five human α(2,3)sialyltransferases, namely ST3Gal -I, -II, -III, -IV and -VI. K{sub M} values for each of these enzymes is presented using radioactivity for acceptors containing Type-I (Galβ1,3GlcNAc), Type-II (Galβ1,4GlcNAc), Type-III (Galβ1,3GalNAc) and Core-2 (Galβ1,3(GlcNAcβ1,6)GalNAc) reactive groups. Several variants of acceptors inhibited ST3Gal activity emphasizing structural role of acceptor in enzyme-catalyzed reactions. In some cases, mass spectrometry was performed for structural verification. The results demonstrate human ST3Gal-I catalysis towards Type-III and Core-2 acceptors with K{submore » M} = 5–50 μM and high V{sub Max} values. The K{sub M} for ST3Gal-I and ST3Gal-II was 100 and 30-fold lower, respectively, for Type-III compared to Type-I acceptors. Variants of Type-I and Type-II structures characterized ST3Gal-III, -IV and -VI for their catalytic specificity. This manuscript also estimates K{sub M} for human ST3Gal-VI using Type-I and Type-II substrates. Together, these findings built a platform for designing inhibitors of STs having therapeutic potential. - Highlights: • K{sub M} for five Human ST3Gals is reported towards Type-I, Type-II & Type-III acceptors. • LC-MS simultaneously quantifies CMP-Neu5Ac & Glycans in a sialylation reaction. • Efficient Core2 sialylation indicates co-operativitiy between ST3Gal-I & C2GnT1. • ST3Gal-I inhibition study proposes iso- or random-sequential bi-bi mechanism.« less

Surface characterisation of ethylene propylene diene rubber upon exposure to aqueous acidic solution

NASA Astrophysics Data System (ADS)

Mitra, Susanta; Ghanbari-Siahkali, Afshin; Kingshott, Peter; Hvilsted, Søren; Almdal, Kristoffer

2006-07-01

Two types of pure ethylene propylene diene rubbers were exposed to two different acids for varying period of time. Surface characterisation was carried out using X-ray photoelectron spectroscopy (XPS). Two EPDM rubbers selected for this study were comparable in co-monomer compositions but significantly different with respect to molar mass and the presence of long chain branching. Both rubbers contained 5-ethylidene-2-norbornene (ENB) as diene. Solution cast films of pure EPDM samples were exposed in two different acidic solutions, viz. chromosulphuric (Cr (VI)/H 2SO 4) and sulphuric acid (H 2SO 4) (20%, v/v) at ambient temperature from 1 to 12 weeks. XPS analysis indicated that several oxygenated species were formed on the surface of both rubbers after exposure. It was postulated from the XPS analyses that both aqueous acidic solutions attacked the olefinic double bonds (C dbnd C) of ENB. Furthermore, 20% Cr (VI)/H 2SO 4 also attacked the allylic carbon-hydrogen (C sbnd H) bonds of ENB resulting in more oxygenated species on the surface compared to 20% H 2SO 4 under identical conditions. Cr (VI) in the 20% Cr (VI)/H 2SO 4 was found to play an important role in alteration of surface chemistry. Studies using a model system consisting of EPDM mixed with Cr (VI) and Cr (III) salts revealed that the change of oxidation state from Cr (VI) to Cr (III) as a consequence of direct involvement of Cr (VI) in the chemical alteration of EPDM surfaces. Interestingly, the presence of long chain branching and molar mass did not significantly influence the chemical processes owing to the acid treatment.

Impact of Group-II Acceptors on the Electrical and Optical Properties of GaN

NASA Astrophysics Data System (ADS)

Lyons, John L.; Janotti, Anderson; Van de Walle, Chris G.

2013-08-01

We explore the properties of group-II acceptors in GaN by performing hybrid density functional calculations. We find that MgGa gives rise to hole localization in zinc-blende GaN, similar to the behavior in the wurtzite phase. Alternative acceptor impurities, such as Zn and Be, also lead to localized holes in wurtzite GaN, and their ionization energies are larger than that of Mg. All these group-II acceptors also cause large lattice distortions in their neutral charge state, which in turn lead to deep and broad luminescence signals. We explore the consequences of these results for p-type doping.

Design of Shallow Acceptors in GaN through Zinc-Magnium Codoping: First-Principles Calculation

NASA Astrophysics Data System (ADS)

Liu, Zhiqiang; Melton, Andrew G.; Yi, Xiaoyan; Wang, Jianwei; Kucukgok, Bahadir; Kang, Jun; Lu, Na; Wang, Junxi; Li, Jinmin; Ferguson, Ian

2013-04-01

In this work, we propose a novel approach to reduce the ionization energy of acceptors in GaN through Zn-Mg codoping. The characteristics of the defect states and the valence-band maximum (VBM) were investigated via first-principles calculation. Our results indicated that the original VBM of the host GaN could be altered by Zn-Mg codoping, thus improving the p-type dopability. We show that the calculated ionization energy ɛ(0/-) of the Zn-Mg acceptor is only 117 meV, which is about 90 meV shallower than that of the isolated Mg acceptor.

Electromembrane extraction of zwitterionic compounds as acid or base: comparison of extraction behavior at acidic and basic pHs.

PubMed

Nojavan, Saeed; Pourahadi, Ahmad; Hosseiny Davarani, Saied Saeed; Morteza-Najarian, Amin; Beigzadeh Abbassi, Mojtaba

2012-10-01

This study has performed on electromembrane extraction (EME) of some zwitterionic compounds based on their acidic and basic properties. High performance liquid chromatography (HPLC) equipped with UV detection was used for determination of model compounds. Cetirizine (CTZ) and mesalazine (MS) were chosen as model compounds, and each of them was extracted from acidic (as a cation) and basic (as an anion) sample solutions, separately. 1-Octanol and 2-nitrophenyl octylether (NPOE) were used as the common supported liquid membrane (SLM) solvents. EME parameters, such as extraction time, extraction voltage and pH of donor and acceptor solutions were studied in details for cationic and anionic forms of each model compound and obtained results for two ionic forms (cationic and anionic) of each compound were compared together. Results showed that zwitterionic compounds could be extracted in both cationic and anionic forms. Moreover, it was found that the extraction of anionic form of each model compound could be done in low voltages when 1-octanol was used as the SLM solvent. Results showed that charge type was not highly effective on the extraction efficiency of model compounds whereas the position of charge within the molecule was the key parameter. In optimized conditions, enrichment factors (EF) of 27-60 that corresponded to recoveries ranging from 39 to 86% were achieved. Copyright © 2012 Elsevier B.V. All rights reserved.

A New Acceptor (N-type) Polyphenylenevinylene Building Block: SF-PPV-I

NASA Technical Reports Server (NTRS)

Wang, Yiqing; Fan, Zhen; Taft, Charles; Sun, Sam-Shajing

2002-01-01

A new sulfone derivatized acceptor (n-type) polyphenylenevinylene "SF-PPV" with nano meter sizes and functional terminals has been synthesized and characterized. The SF-PPV-I that contains hydrocarbon alkyl-sulfone moieties has a strong photoluminescence in both solution and in solid thin film states. In dichloromethane, the 5-10 nm sized SF-PPV has a maximum emission at about 530 nm with excitation maximum at about 490 nm. UV-VIS shows a absorption peak onsite at about 500 nm. Optical spectroscopy and electrochemical studies revealed that the SF-PPV-I has an LUMO level at about -3.6 eV (relative to vacuum), and an HOMO level at about -6.1 eV. The average size (length) of SF-PPV-I can be controlled on the nano meter scale via synthetic means. The SF-PPV has the potential in developing polymer based supramolecular opto-electronic semiconductor devices.

Preparation, spectroscopic and structural studies on charge-transfer complexes of 2,9-dimethyl-1,10-phenanthroline with some electron acceptors

NASA Astrophysics Data System (ADS)

Gaballa, Akmal S.; Wagner, Christoph; Teleb, Said M.; Nour, El-Metwally; Elmosallamy, M. A. F.; Kaluđerović, Goran N.; Schmidt, Harry; Steinborn, Dirk

2008-03-01

Charge-transfer (CT) complexes formed in the reactions of 2,9-dimethyl-1,10-phenanthroline (Me 2phen) with some acceptors such as chloranil (Chl), picric acid (HPA) and chloranilic acid (H 2CA) have been studied in the defined solvent at room temperature. Based on elemental analysis and infrared spectra of the solid CT-complexes along with the photometric titration curves for the reactions, obtained data indicate the formation of 1:1 charge-transfer complexes [(Me 2phen)(Chl)] ( 1), [(Me 2phenH)(PA)] ( 2) and [(Me 2phenH)(HCA)] ( 3), respectively, was proposed. In the three complexes, infrared and 1H NMR spectroscopic data indicate a charge-transfer interaction and as far as complexes 2 and 3 are concerned this interaction is associated with a hydrogen bonding. The formation constants for the complexes ( KC) were shown to be dependent upon the nature of the electron acceptors used. The X-ray structure of complex 3 indicate the formation of dimeric units [Me 2phenH] 2[(HCA) 2] in which the two anions (HCA) - are connected by two O-H⋯O hydrogen bonds whereas the cations and anions are joined together by strong three-center (bifurcated) N-H⋯O hydrogen bonds. Furthermore, the cations are arranged in a π-π stacking.

A hollow-fiber membrane extraction process for recovery and separation of lactic acid from aqueous solution.

PubMed

Huang, Hanjing; Yang, Shang-Tian; Ramey, David E

2004-01-01

An energy-efficient hollow-fiber membrane extraction process was successfully developed to separate and recover lactic acid produced in fermentation. Although many fermentation processes have been developed for lactic acid production, an economical method for lactic acid recovery from the fermentation broth is still needed. Continuous extraction of lactic acid from a simulated aqueous stream was achieved by using Alamine 336 in 2-octanol contained in a hollow-fiber membrane extractor. In this process, the extractant was simultaneously regenerated by stripping with NaOH in a second membrane extractor, and the final product is a concentrated lactate salt solution. The extraction rate increased linearly with an increase in the Alamine 336 content in the solvent (from 5 to 40%). Increasing the concentration of the undissociated lactic acid in the feed solution by either increasing the lactate concentration (from 5 to 40 g/L) or decreasing the solution pH (from 5.0 to 4.0) also increased the extraction rate. Based on these observations, a reactive extraction model with a first-order reaction mechanism for both lactic acid and amine concentrations was proposed. The extraction rate also increased with an increase in the feed flow rate, but not the flow rates of solvent and the stripping solution, suggesting that the process was not limited by diffusion in the liquid films or membrane pores. A mathematical model considering both diffusion and chemical reaction in the extractor and back extractor was developed to simulate the process. The model fits the experimental data well and can be used in scale up design of the process.

Copper-Sulfate Pentahydrate as a Product of the Waste Sulfuric Acid Solution Treatment

NASA Astrophysics Data System (ADS)

Marković, Radmila; Stevanović, Jasmina; Avramović, Ljiljana; Nedeljković, Dragutin; Jugović, Branimir; Stajić-Trošić, Jasna; Gvozdenović, Milica

2012-12-01

The aim of this study is synthesis of copper-sulfate pentahydrate from the waste sulfuric acid solution-mother liquor generated during the regeneration process of copper bleed solution. Copper is removed from the mother liquor solution in the process of the electrolytic treatment using the insoluble lead anodes alloyed with 6 mass pct of antimony on the industrial-scale equipment. As the result of the decopperization process, copper is removed in the form of the cathode sludge and is precipitated at the bottom of the electrolytic cell. By this procedure, the content of copper could be reduced to the 20 mass pct of the initial value. Chemical characterization of the sludge has shown that it contains about 90 mass pct of copper. During the decopperization process, the very strong poison, arsine, can be formed, and the process is in that case terminated. The copper leaching degree of 82 mass pct is obtained using H2SO4 aqueous solution with the oxygen addition during the cathode sludge chemical treatment at 80 °C ± 5 °C. Obtained copper salt satisfies the requirements of the Serbian Standard for Pesticide, SRPS H.P1. 058. Therefore, the treatment of waste sulfuric acid solutions is of great economic and environmental interest.

DISTRIBUTION OF URANIUM, ZIRCONIUM, NIOBIUM, RUTHENIUM AND CERIUM BETWEEN NITRIC ACID SOLUTIONS AND 10% TLA-5% OCTYL ALCOHOL/SHELL SOL-T

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lopez-Menchero, E.; Centeno, J.; Magni, G.

1962-03-01

The extraction of traces of Ru, Zr, Nb, Ce, and U at low concentrations (5 mg/l in aqueous solution) from nitric acid solutions using trilauryl amine (TLA) has been experimentally studied. TLA will eventually be used for final purification of plutonium. Room-temperature data on plutonium contaminant distribution between aqueous solutions of varying nitric acid concentrations and a Shellsol-T solution containing l0% TlA and 5% octyl alcohol are presented. Within the temperature and nitric acid concentration ranges tested, the extractability of uranium increased with increased acid concentrations, although acid concentration in the aqueous phase had no effect on the decontamination factorsmore » for the main fission products. (H.G.G.)« less

Single-subunit oligosaccharyltransferases of Trypanosoma brucei display different and predictable peptide acceptor specificities.

PubMed

Jinnelov, Anders; Ali, Liaqat; Tinti, Michele; Güther, Maria Lucia S; Ferguson, Michael A J

2017-12-08

Trypanosoma brucei causes African trypanosomiasis and contains three full-length oligosaccharyltransferase (OST) genes; two of which, Tb STT3A and Tb STT3B, are expressed in the bloodstream form of the parasite. These OSTs have different peptide acceptor and lipid-linked oligosaccharide donor specificities, and trypanosomes do not follow many of the canonical rules developed for other eukaryotic N -glycosylation pathways, raising questions as to the basic architecture and detailed function of trypanosome OSTs. Here, we show by blue-native gel electrophoresis and stable isotope labeling in cell culture proteomics that the Tb STT3A and Tb STT3B proteins associate with each other in large complexes that contain no other detectable protein subunits. We probed the peptide acceptor specificities of the OSTs in vivo using a transgenic glycoprotein reporter system and performed glycoproteomics on endogenous parasite glycoproteins using sequential endoglycosidase H and peptide: N -glycosidase-F digestions. This allowed us to assess the relative occupancies of numerous N -glycosylation sites by endoglycosidase H-resistant N -glycans originating from Man 5 GlcNAc 2 -PP-dolichol transferred by Tb STT3A, and endoglycosidase H-sensitive N -glycans originating from Man 9 GlcNAc 2 -PP-dolichol transferred by Tb STT3B. Using machine learning, we assessed the features that best define Tb STT3A and Tb STT3B substrates in vivo and built an algorithm to predict the types of N -glycan most likely to predominate at all the putative N -glycosylation sites in the parasite proteome. Finally, molecular modeling was used to suggest why Tb STT3A has a distinct preference for sequons containing and/or flanked by acidic amino acid residues. Together, these studies provide insights into how a highly divergent eukaryote has re-wired protein N -glycosylation to provide protein sequence-specific N -glycan modifications. Data are available via ProteomeXchange with identifiers PXD007236, PXD007267

Significance of a Posttranslational Modification of the PilA Protein of Geobacter sulfurreducens for Surface Attachment, Biofilm Formation, and Growth on Insoluble Extracellular Electron Acceptors.

PubMed

Richter, Lubna V; Franks, Ashley E; Weis, Robert M; Sandler, Steven J

2017-04-15

Geobacter sulfurreducens , an anaerobic metal-reducing bacterium, possesses type IV pili. These pili are intrinsic structural elements in biofilm formation and, together with a number of c -type cytochromes, are thought to serve as conductive nanowires enabling long-range electron transfer (ET) to metal oxides and graphite anodes. Here, we report that a posttranslational modification of a nonconserved amino acid residue within the PilA protein, the structural subunit of the type IV pili, is crucial for growth on insoluble extracellular electron acceptors. Matrix-assisted laser desorption ionization (MALDI) mass spectrometry of the secreted PilA protein revealed a posttranslational modification of tyrosine-32 with a moiety of a mass consistent with a glycerophosphate group. Mutating this tyrosine into a phenylalanine inhibited cell growth with Fe(III) oxides as the sole electron acceptor. In addition, this amino acid substitution severely diminished biofilm formation on graphite surfaces and impaired current output in microbial fuel cells. These results demonstrate that the capability to attach to insoluble electron acceptors plays a crucial role for the cells' ability to utilize them. The work suggests that glycerophosphate modification of Y32 is a key factor contributing to the surface charge of type IV pili, influencing the adhesion of Geobacter to specific surfaces. IMPORTANCE Type IV pili are bacterial appendages that function in cell adhesion, virulence, twitching motility, and long-range electron transfer (ET) from bacterial cells to insoluble extracellular electron acceptors. The mechanism and role of type IV pili for ET in Geobacter sulfurreducens is still a subject of research. In this study, we identified a posttranslational modification of the major G. sulfurreducens type IV pilin, suggested to be a glycerophosphate moiety. We show that a mutant in which the glycerophosphate-modified tyrosine-32 is replaced with a phenylalanine has reduced abilities for

Significance of a Posttranslational Modification of the PilA Protein of Geobacter sulfurreducens for Surface Attachment, Biofilm Formation, and Growth on Insoluble Extracellular Electron Acceptors

PubMed Central

Franks, Ashley E.; Weis, Robert M.; Sandler, Steven J.

2017-01-01

ABSTRACT Geobacter sulfurreducens, an anaerobic metal-reducing bacterium, possesses type IV pili. These pili are intrinsic structural elements in biofilm formation and, together with a number of c-type cytochromes, are thought to serve as conductive nanowires enabling long-range electron transfer (ET) to metal oxides and graphite anodes. Here, we report that a posttranslational modification of a nonconserved amino acid residue within the PilA protein, the structural subunit of the type IV pili, is crucial for growth on insoluble extracellular electron acceptors. Matrix-assisted laser desorption ionization (MALDI) mass spectrometry of the secreted PilA protein revealed a posttranslational modification of tyrosine-32 with a moiety of a mass consistent with a glycerophosphate group. Mutating this tyrosine into a phenylalanine inhibited cell growth with Fe(III) oxides as the sole electron acceptor. In addition, this amino acid substitution severely diminished biofilm formation on graphite surfaces and impaired current output in microbial fuel cells. These results demonstrate that the capability to attach to insoluble electron acceptors plays a crucial role for the cells' ability to utilize them. The work suggests that glycerophosphate modification of Y32 is a key factor contributing to the surface charge of type IV pili, influencing the adhesion of Geobacter to specific surfaces. IMPORTANCE Type IV pili are bacterial appendages that function in cell adhesion, virulence, twitching motility, and long-range electron transfer (ET) from bacterial cells to insoluble extracellular electron acceptors. The mechanism and role of type IV pili for ET in Geobacter sulfurreducens is still a subject of research. In this study, we identified a posttranslational modification of the major G. sulfurreducens type IV pilin, suggested to be a glycerophosphate moiety. We show that a mutant in which the glycerophosphate-modified tyrosine-32 is replaced with a phenylalanine has reduced

Homogeneous freezing of single sulfuric and nitric acid solution drops levitated in an acoustic trap

NASA Astrophysics Data System (ADS)

Diehl, Karoline; Ettner-Mahl, Matthias; Hannemann, Anke; Mitra, Subir K.

2009-10-01

The freezing temperatures of single supercooled drops of binary and ternary sulfuric and nitric acid solutions were measured while varying the acid concentration. An acoustic levitator was used which allows to freely suspend single solution drops in air without electrical charges thereby avoiding any electrical influences which may affect the freezing process. The drops of typically 500 µm in radius were monitored by a video camera during cooling cycles down to - 85 °C to simulate the upper tropospheric and stratospheric temperature range. The present data confirm that liquid solution droplets can be supercooled far below the equilibrium melting point by approximately 35 °C. They follow the general trend of the expected freezing temperatures for homogeneous ice nucleation.

Fluorescent carbon quantum dots synthesized by chemical vapor deposition: An alternative candidate for electron acceptor in polymer solar cells

NASA Astrophysics Data System (ADS)

Cui, Bo; Yan, Lingpeng; Gu, Huimin; Yang, Yongzhen; Liu, Xuguang; Ma, Chang-Qi; Chen, Yongkang; Jia, Husheng

2018-01-01

Excitation-wavelength-dependent blue-greenish fluorescent carbon quantum dots (CQDs) with graphite structure were synthesized by chemical vapor deposition (CVD) method. In comparison with those synthesized by hydrothermal method (named H-CQDs), C-CQDs have less hydrophilic terminal groups, showing good solubility in common organic solvents. Furthermore, these synthesized C-CQDs show a low LUMO energy level (LUMO = -3.84 eV), which is close to that of phenyl-C61-butyric acid methyl ester (PC61BM, LUMO = -4.01 eV), the most widely used electron acceptor in polymer solar cells. Photoluminescence quenching of the poly(3-hexylthiophene-2,5-diyl):C-CQDs blended film (P3HT:C-CQDs) indicated that a photo-induced charge transfer between P3HT and C-CQDs occurs in such a composite film. Bulk heterojunction solar cells using C-CQDs as electron acceptors or doping materials were fabricated and tested. High fill factors were achieved for these C-CQDs based polymer solar cells, demonstrating that CQDs synthesized by CVD could be alternative to the fullerene derivatives for applying in polymer solar cells.

Blinking fluorescence of single donor-acceptor pairs: important role of "dark'' states in resonance energy transfer via singlet levels.

PubMed

Osad'ko, I S; Shchukina, A L

2012-06-01

The influence of triplet levels on Förster resonance energy transfer via singlet levels in donor-acceptor (D-A) pairs is studied. Four types of D-A pair are considered: (i) two-level donor and two-level acceptor, (ii) three-level donor and two-level acceptor, (iii) two-level donor and three-level acceptor, and (iv) three-level donor and three-level acceptor. If singlet-triplet transitions in a three-level acceptor molecule are ineffective, the energy transfer efficiency E=I_{A}/(I_{A}+I_{D}), where I_{D} and I_{A} are the average intensities of donor and acceptor fluorescence, can be described by the simple theoretical equation E(F)=FT_{D}/(1+FT_{D}). Here F is the rate of energy transfer, and T_{D} is the donor fluorescence lifetime. In accordance with the last equation, 100% of the donor electronic energy can be transferred to an acceptor molecule at FT_{D}≫1. However, if singlet-triplet transitions in a three-level acceptor molecule are effective, the energy transfer efficiency is described by another theoretical equation, E(F)=F[over ¯](F)T_{D}/[1+F[over ¯](F)T_{D}]. Here F[over ¯](F) is a function of F depending on singlet-triplet transitions in both donor and acceptor molecules. Expressions for the functions F[over ¯](F) are derived. In this case the energy transfer efficiency will be far from 100% even at FT_{D}≫1. The character of the intensity fluctuations of donor and acceptor fluorescence indicates which of the two equations for E(F) should be used to find the value of the rate F. Therefore, random time instants of photon emission in both donor and acceptor fluorescence are calculated by the Monte Carlo method for all four types of D-A pair. Theoretical expressions for start-stop correlators (waiting time distributions) in donor and acceptor fluorescence are derived. The probabilities w_{N}^{D}(t) and w_{N}^{A}(t) of finding N photons of donor and acceptor fluorescence in the time interval t are calculated for various values of the energy

Quantitative extraction and concentration of synthetic water-soluble acid dyes from aqueous media using a quinine-chloroform solution

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kobayashi, F.; Ozawa, N.; Hanai, J.

Twenty-one water-soluble acid dyes, including eleven azo, five triphenylmethane four xanthene, one naphthol derivatives, used at practical concentrations for food coloration, were quantitatively extracted from water and various carbonated beverages into a 0.1 M quinine-chloroform solution in the presence of 0.5 M boric acid by brief shaking. Quantitative extraction of these dyes was also accomplished by the 0.1 M quinine-chloroform solution made conveniently from chloroform, quinine hydrochloride, and sodium hydroxide added successively to water or beverages containing boric acid. Quinine acted as a countercation on the dyes having sulfonic and/or carboxylic acid group(s) to form chloroform-soluble ion-pair complexes. The diacidicmore » base alkaloid interacted with each acid group of mono-, di-, tri-, and tetrasulfonic acid dyes approximately in the ratio 0.8-0.9 to 1. The dyes in the chloroform solution were quantitatively concentrated into a small volume of sodium hydroxide solution also by brief shaking. The convenient quinine-chloroform method was applicable to the quantitative extraction of a mixture of 12 dyes from carbonated beverages, which are all currently used for food coloration. A high-pressure liquid chromatographic method is also presented for the systematic separation and determination of these 12 dyes following their concentration into the aqueous alkaline solution. The chromatogram was monitored by double-wavelength absorptiometry in the visible and ultraviolet ray regions.« less

Conformation of poly(γ-glutamic acid) in aqueous solution.

PubMed

Muroga, Yoshio; Nakaya, Asami; Inoue, Atsuki; Itoh, Daiki; Abiru, Masaya; Wada, Kaori; Takada, Masako; Ikake, Hiroki; Shimizu, Shigeru

2016-04-01

Local conformation and overall conformation of poly(γ-DL-glutamic acid) (PγDLGA) and poly(γ-L-glutamic acid) (PγLGA) in aqueous solution was studied as a function of degree of ionization ε by (1) H-NMR, circular dichroism, and potentiometric titration. It was clarified that their local conformation is represented by random coil over an entire ε range and their overall conformation is represented by expanded random-coil in a range of ε > ε(*) , where ε(*) is about 0.3, 0.35, 0.45, and 0.5 for added-salt concentration of 0.02M, 0.05M, 0.1M, and 0.2M, respectively. In a range of ε < ε(*) , however, ε dependence of their overall conformation is significantly differentiated from each other. PγDLGA tends to aggregate intramolecularly and/or intermolecularly with decreasing ε, but PγLGA still behaves as expanded random-coil. It is speculated that spatial arrangement of adjacent carboxyl groups along the backbone chain essentially affects the overall conformation of PγGA in acidic media. © 2015 Wiley Periodicals, Inc.

Phase equilibria in a system of aqueous arginine with an octane solution of sulfonic acid

NASA Astrophysics Data System (ADS)

Kuvaeva, Z. I.; Koval'chuk, I. V.; Vodop'yanova, L. A.; Soldatov, V. S.

2013-05-01

The extraction of arginine (Arg) from aqueous salt (0.1 M NaCl) solutions with a sulfo extractant in a wide range of pH values and amino acid concentrations was studied. The 0.1 M solution of dinonylnaphthalenesulfonic acid (HD) in octane was used as an extractant. The degree of extraction was found to be high at pH 0.8-9.0. This can be explained by the effect of additional intermolecular interactions in the extractant phase involving the guanidine group of Arg.

Corrosion Behaviour of Sn-based Lead-Free Solders in Acidic Solution

NASA Astrophysics Data System (ADS)

Nordarina, J.; Mohd, H. Z.; Ahmad, A. M.; Muhammad, F. M. N.

2018-03-01

The corrosion properties of Sn-9(5Al-Zn), Sn-Cu and SAC305 were studied via potentiodynamic polarization method in an acidic solution of 1 M hydrochloric acid (HCl). Sn-9(5Al-Zn) produced different polarization profile compared with Sn-Cu and SAC305. The morphological analysis showed that small, deep grooves shaped of corrosion product formed on top of Sn-9(5Al-Zn) solder while two distinctive structures of closely packed and loosely packed corrosion product formed on top of Sn-Cu and SAC305 solder alloys. Phase analysis revealed the formations of various corrosion products such as SnO and SnO2 mainly dominant on surface of solder alloys after potentiodynamic polarization in 1 M hydrochloric acid (HCl).

Preparation and spectroscopic studies on charge-transfer complexes of 2,2'-bipyridine with picric and chloranilic acids

NASA Astrophysics Data System (ADS)

Teleb, Said M.; Gaballa, Akmal S.

2005-11-01

Charge-transfer (CT) complexes formed on the reaction of 2,2'-bipyridine with some acceptors such as picric acid (HPA) and chloranilic acid (H 2CA) have been studied in CHCl 3 and MeOH at room temperature. Based on elemental analysis and IR spectra of the solid CT complexes along with the photometric titration curves for the reactions, the data obtained indicate the formation of 1:1 charge-transfer complexes [(bpyH)(PA)] and [(bpyH 2)(CA)], respectively. The infrared and 1H NMR spectroscopic data indicate a charge-transfer interaction associated with a proton migration from the acceptor to the donor followed by intramolecular hydrogen bonding. The formation constants ( KC) for the complexes were shown to be dependent on the structure of the electron acceptors used.

Preparation and spectroscopic studies on charge-transfer complexes of 2,2'-bipyridine with picric and chloranilic acids.

PubMed

Teleb, Said M; Gaballa, Akmal S

2005-11-01

Charge-transfer (CT) complexes formed on the reaction of 2,2'-bipyridine with some acceptors such as picric acid (HPA) and chloranilic acid (H(2)CA) have been studied in CHCl(3) and MeOH at room temperature. Based on elemental analysis and IR spectra of the solid CT complexes along with the photometric titration curves for the reactions, the data obtained indicate the formation of 1:1 charge-transfer complexes [(bpyH)(PA)] and [(bpyH(2))(CA)], respectively. The infrared and (1)H NMR spectroscopic data indicate a charge-transfer interaction associated with a proton migration from the acceptor to the donor followed by intramolecular hydrogen bonding. The formation constants (K(C)) for the complexes were shown to be dependent on the structure of the electron acceptors used.

Characterization of a novel sialic acid transporter of the sodium solute symporter (SSS) family and in vivo comparison with known bacterial sialic acid transporters.

PubMed

Severi, Emmanuele; Hosie, Arthur H F; Hawkhead, Judith A; Thomas, Gavin H

2010-03-01

The function of sialic acids in the biology of bacterial pathogens is reflected by the diverse range of solute transporters that can recognize these sugar acids. Here, we use an Escherichia coliDeltananT strain to characterize the function of known and proposed bacterial sialic acid transporters. We discover that the STM1128 gene from Salmonella enterica serovar Typhimurium, which encodes a member of the sodium solute symporter family, is able to restore growth on sialic acid to the DeltananT strain and is able to transport [(14)C]-sialic acid. Using the DeltananT genetic background, we performed a direct in vivo comparison of the transport properties of the STM1128 protein with those of sialic acid transporters of the major facilitator superfamily and tripartite ATP-independent periplasmic families, E. coli NanT and Haemophilus influenzae SiaPQM, respectively. This revealed that both STM1128 and SiaPQM are sodium-dependent and, unlike SiaPQM, both STM1128 and NanT are reversible secondary carriers, demonstrating qualitative functional differences in the properties of sialic acid transporters used by bacteria that colonize humans.

Electronic spectrum of non-tetrahedral acceptors in CdTe:Cl and CdTe:Bi,Cl single crystals

DOE Office of Scientific and Technical Information (OSTI.GOV)

Krivobok, V. S., E-mail: krivobok@lebedev.ru; Moscow Institute of Physics and Technology; Nikolaev, S. N.

2016-02-07

The electronic spectra of complex acceptors in compensated CdTe:Cl, CdTe:Ag,Cl, and CdTe:Bi,Cl single crystals are studied using low-temperature photoluminescence (PL) measurements under both nonresonant and resonant excitation of distant donor–acceptor pairs (DAP). The wavelength modulation of the excitation source combined with the analysis of the differential PL signal is used to enhance narrow spectral features obscured because of inhomogeneous line broadening and/or excitation transfer for selectively excited DAPs. For the well-known tetrahedral (T{sub D}) Ag{sub Cd} acceptor, the energies of four excited states are measured, and the values obtained are shown to be in perfect agreement with the previous data.more » Moreover, splitting between the 2P{sub 3/2} (Γ{sub 8}) and 2S{sub 3/2} (Γ{sub 8}) states is clearly observed for Ag{sub Cd} centers located at a short distance (5–7 nm) from a hydrogen-like donor (Cl{sub Te}). This splitting results from the reduction of the T{sub D} symmetry taking place when the acceptor is a member of a donor–acceptor pair. For the Cl-related complex acceptor with an activation energy of ∼121 meV (A-center), the energies of eight excited states are measured. It is shown that this defect produces low-symmetry central-cell correction responsible for the strong splitting of S-like T{sub D} shells. The energy spectrum of the Bi-related shallow acceptor with an activation energy of ∼36 meV is measured as well. The spectrum obtained differs drastically from the hydrogen-like set of levels, which indicates the existence of repulsive low-symmetry perturbation of the hydrogen-like Coulomb potential. It is also shown that the spectra of selectively excited PL recorded for a macroscopic ensemble of distant donor–acceptor pairs allow one to detect the low symmetry of acceptors of a given type caused by their complex nature or by the Jahn–Teller distortion. This method does not require any additional (external) field

Donor-bridge-acceptor energetics determine the distance dependence of electron tunneling in DNA

NASA Astrophysics Data System (ADS)

Lewis, Frederick D.; Liu, Jianqin; Weigel, Wilfried; Rettig, Wolfgang; Kurnikov, Igor V.; Beratan, David N.

2002-10-01

Electron transfer (ET) processes in DNA are of current interest because of their involvement in oxidative strand cleavage reactions and their relevance to the development of molecular electronics. Two mechanisms have been identified for ET in DNA, a single-step tunneling process and a multistep charge-hopping process. The dynamics of tunneling reactions depend on both the distance between the electron donor and acceptor and the nature of the molecular bridge separating the donor and acceptor. In the case of protein and alkane bridges, the distance dependence is not strongly dependent on the properties of the donor and acceptor. In contrast, we show here that the distance decay of DNA ET rates varies markedly with the energetics of the donor and acceptor relative to the bridge. Specifically, we find that an increase in the energy of the bridge states by 0.25 eV (1 eV = 1.602 × 1019 J) relative to the donor and acceptor energies for photochemical oxidation of nucleotides, without changing the reaction free energy, results in an increase in the characteristic exponential distance decay constant for the ET rates from 0.71 to 1.1 Å1. These results show that, in the small tunneling energy gap regime of DNA ET, the distance dependence is not universal; it varies strongly with the tunneling energy gap. These DNA ET reactions fill a "missing link" or transition regime between the large barrier (rapidly decaying) tunneling regime and the (slowly decaying) hopping regime in the general theory of bridge-mediated ET processes.

Solution blow spun Poly(lactic acid)/Hydroxypropyl methylcellulose nanofibers with antimicrobial properties

USDA-ARS?s Scientific Manuscript database

Poly(lactic acid) (PLA) nanofibers containing hydroxypropyl methylcellulose (HPMC) and tetracycline hydrochloride (THC) were solution blow spun from two different solvents, chloroform/acetone (CA, 80:20 v/v) and 2,2,2-triflouroethanol (TFE). The diameter distribution, chemical, thermal, thermal stab...

The solute carrier family 10 (SLC10): beyond bile acid transport

PubMed Central

da Silva, Tatiana Claro; Polli, James E.; Swaan, Peter W.

2012-01-01

The solute carrier (SLC) family 10 (SLC10) comprises influx transporters of bile acids, steroidal hormones, various drugs, and several other substrates. Because the seminal transporters of this family, namely, sodium/taurocholate cotransporting polypeptide (NTCP; SLC10A1) and the apical sodium-dependent bile acid transporter (ASBT; SLC10A2), were primarily bile acid transporters, the term “sodium bile salt cotransporting family” was used for the SLC10 family. However, this notion became obsolete with the finding of other SLC10 members that do not transport bile acids. For example, the sodium-dependent organic anion transporter (SOAT; SLC10A6) transports primarily sulfated steroids. Moreover, NTCP was shown to also transport steroids and xenobiotics, including HMG-CoA inhibitors (statins). The SLC10 family contains four additional members, namely, P3 (SLC10A3; SLC10A3), P4 (SLC10A4; SLC10A4), P5 (SLC10A5; SLC10A5) and SLC10A7 (SLC10A7), several of which were unknown or considered hypothetical until approximately a decade ago. While their substrate specificity remains undetermined, great progress has been made towards their characterization in recent years. SLC10A4 may participate in vesicular storage or exocytosis of neurotransmitters or mastocyte mediators, whereas SLC10A5 and SLC10A7 may be involved in solute transport and SLC10A3 may have a role as a housekeeping protein. Finally, the newly found role of bile acids in glucose and energy homeostasis, via the TGR5 receptor, sheds new light on the clinical relevance of ASBT and NTCP. The present mini-review provides a brief summary of recent progress on members of the SLC10 family. PMID:23506869

A decade of monitoring at Swiss Long-Term Forest Ecosystem Research (LWF) sites: can we observe trends in atmospheric acid deposition and in soil solution acidity?

PubMed

Pannatier, Elisabeth Graf; Thimonier, Anne; Schmitt, Maria; Walthert, Lorenz; Waldner, Peter

2011-03-01

Trends in atmospheric acid deposition and in soil solution acidity from 1995 or later until 2007 were investigated at several forest sites throughout Switzerland to assess the effects of air pollution abatements on deposition and the response of the soil solution chemistry. Deposition of the major elements was estimated from throughfall and bulk deposition measurements at nine sites of the Swiss Long-Term Forest Ecosystem Research network (LWF) since 1995 or later. Soil solution was measured at seven plots at four soil depths since 1998 or later. Trends in the molar ratio of base cations to aluminum (BC/Al) in soil solutions and in concentrations and fluxes of inorganic N (NO(3)-N + NH(4)-N), sulfate (SO(4)-S), and base cations (BC) were used to detect changes in soil solution chemistry. Acid deposition significantly decreased at three out of the nine study sites due to a decrease in total N deposition. Total SO(4)-S deposition decreased at the nine sites, but due to the relatively low amount of SO(4)-S load compared to N deposition, it did not contribute to decrease acid deposition significantly. No trend in total BC deposition was detected. In the soil solution, no trend in concentrations and fluxes of BC, SO(4)-S, and inorganic N were found at most soil depths at five out of the seven sites. This suggests that the soil solution reacted very little to the changes in atmospheric deposition. A stronger reduction in base cations compared to aluminum was detected at two sites, which might indicate that acidification of the soil solution was proceeding faster at these sites.

GADOLINIUM OXALATE SOLUBILITY MEASUREMENTS IN NITRIC ACID SOLUTIONS

DOE Office of Scientific and Technical Information (OSTI.GOV)

Pierce, R. A.

2012-03-12

HB-Line will begin processing Pu solutions during FY2012 that will involve the recovery of Pu using oxalate precipitation and filtration. After the precipitation and filtration processes, the filtrate solution will be transferred from HB-Line to H-Canyon. The presence of excess oxalate and unfiltered Pu oxalate solids in these solutions create a criticality safety issue if they are sent to H-Canyon without controls in H-Canyon. One approach involves H-Canyon receiving the filtrate solution into a tank that is poisoned with soluble gadolinium (Gd). Decomposition of the oxalate will occur within a subsequent H-Canyon vessel. The receipt of excess oxalate into themore » H-Canyon receipt tanks has the potential to precipitate a portion of the Gd poison in the receipt tanks. Because the amount of Gd in solution determines the maximum amount of Pu solids that H-Canyon can receive, H-Canyon Engineering requested that SRNL determine the solubility of Gd in aqueous solutions of 4-10 M nitric acid (HNO{sub 3}), 4-12 g/L Gd, and 0.15-0.25 M oxalic acid (H{sub 2}C{sub 2}O{sub 4}) at 25 °C. The target soluble Gd concentration is 6 g/L. The data indicate that the target can be achieved above 6 M HNO{sub 3} and below 0.25 M H{sub 2}C{sub 2}O{sub 4}. At 25 °C, for 6 M HNO{sub 3}, 11 g/L and 7 g/L Gd are soluble in 0.15 M and 0.25 M H{sub 2}C{sub 2}O{sub 4}, respectively. In 4 M HNO{sub 3}, the Gd solubility drops significantly to 2.5 g/L and 0.8 g/L in 0.15 M and 0.25 M H{sub 2}C{sub 2}O{sub 4}, respectively. The solubility of Gd at 8-10 M HNO{sub 3} exceeds the solubility at 6 M HNO{sub 3}. The data for 4 M HNO{sub 3} showed good agreement with data in the literature. To achieve a target of 6 g/L soluble Gd in solution in the presence of 0.15-0.25 M oxalate, the HNO{sub 3} concentration must be maintained at or above 6 M HNO{sub 3}. The solubility of Gd in 4 M HNO{sub 3} with 0.15 M oxalate at 10 °C is about 1.5 g/L. For 6 M HNO{sub 3} with 0.15 M oxalate, the solubility of

Chemical durability of glaze on Zsolnay architectural ceramics (Budapest, Hungary) in acid solutions

NASA Astrophysics Data System (ADS)

Baricza, Ágnes; Bajnóczi, Bernadett; May, Zoltán; Tóth, Mária; Szabó, Csaba

2015-04-01

Zsolnay glazed architectural ceramics are among the most famous Hungarian ceramics, however, there is no profound knowledge about the deterioration of these building materials. The present study aims to reveal the influence of acidic solutions in the deterioration of Zsolnay ceramics. The studied ceramics are glazed roof tiles, which originate from two buildings in Budapest: one is located in the densely built-up city centre with high traffic rate and another one is in a city quarter with moderate traffic and more open space. The roof tiles represent the construction and the renovation periods of the buildings. The ceramics were mainly covered by lead glazes in the construction period and mainly alkali glazes in the renovation periods. The glaze of the tiles were coloured with iron (for yellow glaze) or chromium/copper/iron (for green glazes) in the case of the building located in the city centre, whereas cobalt was used as colorant and tin oxide as opacifier for the blue glaze of the ceramics of the other building. Six tiles were selected from each building. Sulphuric acid (H2SO4) solutions of pH2 and pH4 were used to measure the durability of the glazes up to 14 days at room temperature. The surfaces of the glazed ceramics after the treatment were measured by X-ray diffraction, Raman spectroscopy and SEM-EDS techniques to determine the precipitated phases on the surface of the glaze. Electron microprobe analysis was used to quantitatively characterise phases found and to determine the chemical composition of the treated glaze. The recovered sulphuric acid solutions were measured with ICP-OES technique in order to quantify the extent of the ion exchange between the glaze and the solutions. There is a significant difference in the dissolution rates in the treatments with sulphuric acid solutions of pH2 and pH4, respectively. The solution of pH2 induced greater ion exchange (approx. 7-10 times) from the glaze compared to the solution of pH4. Alkali and alkali earth

Chemical and spectral behavior of nitric acid in aqueous sulfuric acid solutions: Absorption spectrum and molar absorption coefficient of nitronium ion

NASA Astrophysics Data System (ADS)

Ershov, Boris G.; Panich, Nadezhda M.

2018-01-01

The chemical species formed from nitric acid in aqueous solutions of sulfuric acid (up to 18.0 mol L- 1) were studied by optical spectroscopy method. The concentration region of nitronium ion formation was identified and NO2+ ion absorption spectrum was measured (λmax ≤ 190 nm and ε190 = 1040 ± 50 mol- 1 L cm- 1).

Generalization of the Förster resonance energy transfer theory for quantum mechanical modulation of the donor-acceptor coupling

NASA Astrophysics Data System (ADS)

Jang, Seogjoo

2007-11-01

The Förster resonance energy transfer theory is generalized for inelastic situations with quantum mechanical modulation of the donor-acceptor coupling. Under the assumption that the modulations are independent of the electronic excitation of the donor and the acceptor, a general rate expression is derived, which involves two dimensional frequency-domain convolution of the donor emission line shape, the acceptor absorption line shape, and the spectral density of the modulation of the donor-acceptor coupling. For two models of modulation, detailed rate expressions are derived. The first model is the fluctuation of the donor-acceptor distance, approximated as a quantum harmonic oscillator coupled to a bath of other quantum harmonic oscillators. The distance fluctuation results in additional terms in the rate, which in the small fluctuation limit depend on the inverse eighth power of the donor-acceptor distance. The second model is the fluctuation of the torsional angle between the two transition dipoles, which is modeled as a quantum harmonic oscillator coupled to a bath of quantum harmonic oscillators and causes sinusoidal modulation of the donor-acceptor coupling. The rate expression has new elastic and inelastic terms, depending sensitively on the value of the minimum energy torsional angle. Experimental implications of the present theory and some of the open theoretical issues are discussed.

Molecular complexes of alprazolam with carboxylic acids, boric acid, boronic acids, and phenols. Evaluation of supramolecular heterosynthons mediated by a triazole ring.

PubMed

Varughese, Sunil; Azim, Yasser; Desiraju, Gautam R

2010-09-01

A series of molecular complexes, both co-crystals and salts, of a triazole drug-alprazolam-with carboxylic acids, boric acid, boronic acids, and phenols have been analyzed with respect to heterosynthons present in the crystal structures. In all cases, the triazole ring behaves as an efficient hydrogen bond acceptor with the acidic coformers. The hydrogen bond patterns exhibited with aromatic carboxylic acids were found to depend on the nature and position of the substituents. Being a strong acid, 2,6-dihydroxybenzoic acid forms a salt with alprazolam. With aliphatic dicarboxylic acids alprazolam forms hydrates and the water molecules play a central role in synthon formation and crystal packing. The triazole ring makes two distinct heterosynthons in the molecular complex with boric acid. Boronic acids and phenols form consistent hydrogen bond patterns, and these are seemingly independent of the substitutional effects. Boronic acids form noncentrosymmetric cyclic synthons, while phenols form O--H...N hydrogen bonds with the triazole ring.

Förster Resonance Energy Transfer between Quantum Dot Donors and Quantum Dot Acceptors

PubMed Central

Chou, Kenny F.; Dennis, Allison M.

2015-01-01

Förster (or fluorescence) resonance energy transfer amongst semiconductor quantum dots (QDs) is reviewed, with particular interest in biosensing applications. The unique optical properties of QDs provide certain advantages and also specific challenges with regards to sensor design, compared to other FRET systems. The brightness and photostability of QDs make them attractive for highly sensitive sensing and long-term, repetitive imaging applications, respectively, but the overlapping donor and acceptor excitation signals that arise when QDs serve as both the donor and acceptor lead to high background signals from direct excitation of the acceptor. The fundamentals of FRET within a nominally homogeneous QD population as well as energy transfer between two distinct colors of QDs are discussed. Examples of successful sensors are highlighted, as is cascading FRET, which can be used for solar harvesting. PMID:26057041

Corrosion behavior of ODS steels with several chromium contents in hot nitric acid solutions

NASA Astrophysics Data System (ADS)

Tanno, Takashi; Takeuchi, Masayuki; Ohtsuka, Satoshi; Kaito, Takeji

2017-10-01

Oxide dispersion strengthened (ODS) steel cladding tubes have been developed for fast reactors. Tempered martensitic ODS steels with 9 and 11 wt% of chromium (9Cr-, 11Cr-ODS steel) are the candidate material in research being carried out at JAEA. In this work, fundamental immersion tests and electrochemical tests of 9 to 12Cr-ODS steels were systematically conducted in various nitric acid solutions at 95 °C. The corrosion rate decreased exponentially with effective solute chromium concentration (Creff) and nitric acid concentration. Addition of vanadium (V) and ruthenium (Ru) also decreased the corrosion rate. The combination of low Creff and dilute nitric acid could not avoid the active mass dissolution during active domain at the beginning of immersion, and the corrosion rate was high. Higher Creff decreased the partial anodic current during the active domain and assisted the passivation of the surface of the steel. Concentrated nitric acid and addition of Ru and V increased partial cathodic current and shifted the corrosion potential to noble side. These effects should have prevented the active mass dissolution and decreased the corrosion rate.

Unified molecular picture of the surfaces of aqueous acid, base, and salt solutions.

PubMed

Mucha, Martin; Frigato, Tomaso; Levering, Lori M; Allen, Heather C; Tobias, Douglas J; Dang, Liem X; Jungwirth, Pavel

2005-04-28

The molecular structure of the interfacial regions of aqueous electrolytes is poorly understood, despite its crucial importance in many biological, technological, and atmospheric processes. A long-term controversy pertains between the standard picture of an ion-free surface layer and the strongly ion specific behavior indicating in many cases significant propensities of simple inorganic ions for the interface. Here, we present a unified and consistent view of the structure of the air/solution interface of aqueous electrolytes containing monovalent inorganic ions. Molecular dynamics calculations show that in salt solutions and bases the positively charged ions, such as alkali cations, are repelled from the interface, whereas the anions, such as halides or hydroxide, exhibit a varying surface propensity, correlated primarily with the ion polarizability and size. The behavior of acids is different due to a significant propensity of hydronium cations for the air/solution interface. Therefore, both cations and anions exhibit enhanced concentrations at the surface and, consequently, these acids (unlike bases and salts) reduce the surface tension of water. The results of the simulations are supported by surface selective nonlinear vibrational spectroscopy, which reveals among other things that the hydronium cations are present at the air/solution interface. The ion specific propensities for the air/solution interface have important implications for a whole range of heterogeneous physical and chemical processes, including atmospheric chemistry of aerosols, corrosion processes, and bubble coalescence.

The ETHANOL-CO_2 Dimer is AN Electron Donor-Acceptor Complex

NASA Astrophysics Data System (ADS)

McGuire, Brett A.; Martin-Drumel, Marie-Aline; McCarthy, Michael C.

2017-06-01

Supercritical (sc) CO_2 is a common industrial solvent for the extraction of caffeine, nicotine, petrochemicals, and natural products. The ability of apolar scCO_2 to dissolve polar solutes is greatly enhanced by the addition of a polar co-solvent, often methanol or ethanol. Experimental and theoretical work show that methanol interactions in scCO_2 are predominantly hydrogen bonding, while the gas-phase complex is an electron donor-acceptor (EDA) configuration. Ethanol, meanwhile, is predicted to form EDA complexes both in scCO_2 and in the gas phase, but there have been no experimental measurements to support this conclusion. Here, we report a combined chirped-pulse and cavity FTMW study of the ethanol-CO_2 complex. Comparison with theory indicates the EDA complex is dominant under our experimental conditions. We confirm the structure with isotopic substitution, and derive a semi-experimental equilibrium structure. Our results are consistent with theoretical predictions that the linearity of the CO_2 subgroup is broken by the complexation interaction.

Absorption and emission behaviour of trans- p-coumaric acid in aqueous solutions and some organic solvents

NASA Astrophysics Data System (ADS)

Putschögl, M.; Zirak, P.; Penzkofer, A.

2008-01-01

The absorption and fluorescence behaviour of trans- p-coumaric acid ( trans-4-hydroxycinnamic acid) is investigated in buffered aqueous solution over a wide range from pH 1 to pH 12, in un-buffered water, and in some organic solvents. Absorption cross-section spectra, fluorescence quantum distributions, fluorescence quantum yields, and degrees of fluorescence polarisation are measured. p-Coumaric acid exists in different ionic forms in aqueous solution depending on the pH. There is an equilibrium between the neutral form ( p-CAH 2) and the single anionic form ( p-CAH -) at low pH (p Kna ≈ 4.9), and between the single anionic and the double anionic form ( p-CA 2-) at high pH (p Kaa ≈ 9.35). In the organic solvents studied trans- p-coumaric acid is dissolved in its neutral form. The fluorescence quantum yield of trans- p-coumaric acid in aqueous solution is ϕF ≈ 1.4 × 10 -4 for the neutral and the single anionic form, while it is ϕF ≈ 1.3 × 10 -3 for the double anionic form. For trans- p-coumaric acid in organic solvents fluorescence quantum yields in the range from 4.8 × 10 -5 (acetonitrile) to 1.5 × 10 -4 (glycerol) were measured. The fluorescence spectra are 7700-10,000 cm -1 Stokes shifted in aqueous solution, and 5400-8200 cm -1 Stokes shifted in the studied organic solvents. Decay paths responsible for the low fluorescence quantum yields are discussed (photo-isomerisation and internal conversion for p-CA 2-, solvent-assisted intra-molecular charge-transfer or ππ ∗ to nπ ∗ transfer and internal conversion for p-CAH 2 and p-CAH -). The solvent dependence of the first ππ ∗ electronic transition frequency and of the fluorescence Stokes shift of p-CAH 2 is discussed in terms of polar solute-solvent interaction effects. Thereby the ground-state and excite-state molecular dipole moments are extracted.

Reduction in bacterial load using hypochlorous acid hygiene solution on ocular skin

PubMed Central

Stroman, David W; Mintun, Keri; Epstein, Arthur B; Brimer, Crystal M; Patel, Chirag R; Branch, James D; Najafi-Tagol, Kathryn

2017-01-01

Purpose To examine the magnitude of bacterial load reduction on the surface of the periocular skin 20 minutes after application of a saline hygiene solution containing 0.01% pure hypochlorous acid (HOCl). Methods Microbiological specimens were collected immediately prior to applying the hygiene solution and again 20 minutes later. Total microbial colonies were counted and each unique colony morphology was processed to identify the bacterial species and to determine the susceptibility profile to 15 selected antibiotics. Results Specimens were analyzed from the skin samples of 71 eyes from 36 patients. Prior to treatment, 194 unique bacterial isolates belonging to 33 different species were recovered. Twenty minutes after treatment, 138 unique bacterial isolates belonging to 26 different species were identified. Staphylococci accounted for 61% of all strains recovered and Staphylococcus epidermidis strains comprised 60% of the staphylococcal strains. No substantial differences in the distribution of Gram-positive, Gram-negative, or anaerobic species were noted before and after treatment. The quantitative data demonstrated a >99% reduction in the staphylococcal load on the surface of the skin 20 minutes following application of the hygiene solution. The total S. epidermidis colony-forming units were reduced by 99.5%. The HOCl hygiene solution removed staphylococcal isolates that were resistant to multiple antibiotics equally well as those isolates that were susceptible to antibiotics. Conclusion The application of a saline hygiene solution preserved with pure HOCl acid reduced the bacterial load significantly without altering the diversity of bacterial species remaining on the skin under the lower eyelid. PMID:28458509

49 CFR 173.195 - Hydrogen cyanide, anhydrous, stabilized (hydrocyanic acid, aqueous solution).

Code of Federal Regulations, 2013 CFR

2013-10-01

... 49 Transportation 2 2013-10-01 2013-10-01 false Hydrogen cyanide, anhydrous, stabilized... Hazardous Materials Other Than Class 1 and Class 7 § 173.195 Hydrogen cyanide, anhydrous, stabilized (hydrocyanic acid, aqueous solution). (a) Hydrogen cyanide, anhydrous, stabilized, must be packed in...

49 CFR 173.195 - Hydrogen cyanide, anhydrous, stabilized (hydrocyanic acid, aqueous solution).

Code of Federal Regulations, 2011 CFR

2011-10-01

... 49 Transportation 2 2011-10-01 2011-10-01 false Hydrogen cyanide, anhydrous, stabilized... Hazardous Materials Other Than Class 1 and Class 7 § 173.195 Hydrogen cyanide, anhydrous, stabilized (hydrocyanic acid, aqueous solution). (a) Hydrogen cyanide, anhydrous, stabilized, must be packed in...

49 CFR 173.195 - Hydrogen cyanide, anhydrous, stabilized (hydrocyanic acid, aqueous solution).

Code of Federal Regulations, 2010 CFR

2010-10-01

... 49 Transportation 2 2010-10-01 2010-10-01 false Hydrogen cyanide, anhydrous, stabilized... Hazardous Materials Other Than Class 1 and Class 7 § 173.195 Hydrogen cyanide, anhydrous, stabilized (hydrocyanic acid, aqueous solution). (a) Hydrogen cyanide, anhydrous, stabilized, must be packed in...

49 CFR 173.195 - Hydrogen cyanide, anhydrous, stabilized (hydrocyanic acid, aqueous solution).

Code of Federal Regulations, 2012 CFR

2012-10-01

... 49 Transportation 2 2012-10-01 2012-10-01 false Hydrogen cyanide, anhydrous, stabilized... Hazardous Materials Other Than Class 1 and Class 7 § 173.195 Hydrogen cyanide, anhydrous, stabilized (hydrocyanic acid, aqueous solution). (a) Hydrogen cyanide, anhydrous, stabilized, must be packed in...

49 CFR 173.195 - Hydrogen cyanide, anhydrous, stabilized (hydrocyanic acid, aqueous solution).

Code of Federal Regulations, 2014 CFR

2014-10-01

... 49 Transportation 2 2014-10-01 2014-10-01 false Hydrogen cyanide, anhydrous, stabilized... Hazardous Materials Other Than Class 1 and Class 7 § 173.195 Hydrogen cyanide, anhydrous, stabilized (hydrocyanic acid, aqueous solution). (a) Hydrogen cyanide, anhydrous, stabilized, must be packed in...

Acceptor number-dependent ultrafast photo-physical properties of push-pull chromophores using time-resolved methods

NASA Astrophysics Data System (ADS)

Chi, Xiao-Chun; Wang, Ying-Hui; Gao, Yu; Sui, Ning; Zhang, Li-Quan; Wang, Wen-Yan; Lu, Ran; Ji, Wen-Yu; Yang, Yan-Qiang; Zhang, Han-Zhuang

2018-04-01

Three push-pull chromophores comprising a triphenylamine (TPA) as electron-donating moiety and functionalized β-diketones as electron acceptor units are studied by various spectroscopic techniques. The time-correlated single-photon counting data shows that increasing the number of electron acceptor units accelerates photoluminescence relaxation rate of compounds. Transient spectra data shows that intramolecular charge transfer (ICT) takes place from TPA units to β-diketones units after photo-excitation. Increasing the number of electron acceptor units would prolong the generation process of ICT state, and accelerate the excited molecule reorganization process and the relaxation process of ICT state.

Design of donor-acceptor copolymers for organic photovoltaic materials: a computational study.

PubMed

Turan, Haydar Taylan; Kucur, Oğuzhan; Kahraman, Birce; Salman, Seyhan; Aviyente, Viktorya

2018-01-31

80 different push-pull type organic chromophores which possess Donor-Acceptor (D-A) and Donor-Thiophene-Acceptor-Thiophene (D-T-A-T) structures have been systematically investigated by means of density functional theory (DFT) and time-dependent DFT (TD-DFT) at the B3LYP/6-311G* level. The introduction of thiophene (T) in the chain has allowed us to monitor the effect of π-spacers. Benchmark studies on the methodology have been carried out to predict the HOMO and LUMO energies and optical band gaps of the D-A systems accurately. The HOMO and LUMO energies and transition dipoles are seen to converge for tetrameric oligomers, and the latter have been used as optimal chain length to evaluate various geometrical and optoelectronic properties such as bond length alternations, distortion energies, frontier molecular orbital energies, reorganization energies and excited-state vertical transition of the oligomers. Careful analysis of our findings has allowed us to propose potential donor-acceptor couples to be used in organic photovoltaic cells.

Spectroscopic investigations of the charge-transfer interaction between the drug reserpine and different acceptors: Towards understanding of drug-receptor mechanism

NASA Astrophysics Data System (ADS)

Eldaroti, Hala H.; Gadir, Suad A.; Refat, Moamen S.; Adam, Abdel Majid A.

2013-11-01

The study of the charge-transfer interaction of the drugs may be useful in understanding the drug-receptor interactions and the mechanism of drug action. Structural and thermal stability of charge-transfer (CT) complexes formed between the drug reserpine (Res) as a donor and quinol (QL), picric acid (PA), tetracyanoquinodimethane (TCNQ) or dichlorodicyanobenzoquinone (DDQ) as acceptors were reported. Elemental analysis, electronic absorption, spectrophotometric titration, IR, Raman, 1H NMR and X-ray powder diffraction (XRD) were used to characterize the new products. The thermal stability of the synthesized CT complexes was investigated using thermogravimetric (TG) analyses, and the morphology and particle size of these complexes were obtained from scanning electron microscopy (SEM). The stoichiometry of the complexes (donor:acceptor molar ratio) was determined to be 1:1 for all complexes. Accordingly the formed CT complexes could be formulated as [(Res)(QL)], [(Res)(PA)], [(Res)(TCNQ)] and [(Res)(DDQ)]. It was found that the obtained CT complexes are nanoscale, semi-crystalline particles, thermally stable and formed through spontaneous reaction. The results obtained herein are satisfactory for estimation of drug Res in the pharmaceutical form.

Charge transfer complex of some nervous and brain drugs - Part 1: Synthesis, spectroscopic, analytical and biological studies on the reaction between haloperidol antipsychotic drugs with π-acceptors

NASA Astrophysics Data System (ADS)

El-Habeeb, Abeer A.; Al-Saif, Foziah A.; Refat, Moamen S.

2013-02-01

Donor-acceptor interactions between the electron donor haloperidol (HPL) and π-acceptors like 7,7,8,8-tetracyanoquinodimethane (TCNQ) and picric acid (PA) have been studied spectrophotometrically in CH3OH solvent. The donor-acceptor (charge transfer complexes) were discussed in terms of formation constant (KCT), molar extinction coefficient (ɛCT), standard free energy (ΔGo), oscillator strength (ƒ), transition dipole moment (μ), resonance energy (RN) and ionization potential (ID). The stoichiometry of these complexes was found to be 1:1 M ratio and having the formulas [(HPL)(TCNQ)] and [(HPL)(PA)], respectively. The charge transfer interaction was successfully applied to determine of HPL drug using mentioned common π-acceptors also, the results obtained herein are satisfactory for estimation of HPL compound in the pharmaceutical form. The formed solid charge-transfer complexes were also isolated and characterized using elemental analysis, conductivity, (infrared, Raman, and 1H NMR) spectra and X-ray powder diffraction (XRD). The experimental data of elemental analyses are in agreement with calculated data. The infrared spectra of both HPL complexes are confirming the participation of sbnd OH of 4-hydroxy-1-piperidyl moiety in the donor-acceptor chelation. The morphological surface of the resulted charge transfer complexes were investigated using scanning electron microscopy (SEM). The thermogravimetric analysis (TG/DTG) and differential scanning calorimetry (DSC) techniques were performed to give knowledge about the thermal stability behavior of the synthesized charge transfer complexes. Thermodynamic parameters were computed from the thermal decomposition data. These complexes were also tested for their antimicrobial activity against six different microorganisms, and the results were compared with the parent drug.

Synthesis of highly ordered TiO2 nanotube in malonic acid solution by anodization.

PubMed

Ryu, Won Hee; Park, Chan Jin; Kwon, Hyuk Sang

2008-10-01

We synthesized TiO2 nanotube array by anodizing in a solution of malonic acid (HOOCCH2COOH) and NH4F, and analyzed the morphology of the nanotube using scanning electron microscopy (SEM). The morphology of TiO2 nanotube was largely affected by anodizing time, anodizing voltage, and malonic acid concentration. With increasing the anodizing voltage from 5 V to 20 V, the diameter of TiO2 nanotube was increased from about 20 nm to 110 nm and its length from about 10 nm to 700 nm. In addition, the length of TiO2 nanotube was increased with increasing anodizing time up to 6 h at 20 V. We obtained the longest and the most highly ordered nanotube structure when anodizing Ti in a solution of 0.5 wt% NH4F and 1 M malonic acid at 20 V for 6 h.

Fullerene derivatives as electron acceptors for organic photovoltaic cells.

PubMed

Mi, Dongbo; Kim, Ji-Hoon; Kim, Hee Un; Xu, Fei; Hwang, Do-Hoon

2014-02-01

Energy is currently one of the most important problems humankind faces. Depletion of traditional energy sources such as coal and oil results in the need to develop new ways to create, transport, and store electricity. In this regard, the sun, which can be considered as a giant nuclear fusion reactor, represents the most powerful source of energy available in our solar system. For photovoltaic cells to gain widespread acceptance as a source of clean and renewable energy, the cost per watt of solar energy must be decreased. Organic photovoltaic cells, developed in the past two decades, have potential as alternatives to traditional inorganic semiconductor photovoltaic cells, which suffer from high environmental pollution and energy consumption during production. Organic photovoltaic cells are composed of a blended film of a conjugated-polymer donor and a soluble fullerene-derivative acceptor sandwiched between a poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate)-coated indium tin oxide positive electrode and a low-work-function metal negative electrode. Considerable research efforts aim at designing and synthesizing novel fullerene derivatives as electron acceptors with up-raised lowest unoccupied molecular orbital energy, better light-harvesting properties, higher electron mobility, and better miscibility with the polymer donor for improving the power conversion efficiency of the organic photovoltaic cells. In this paper, we systematically review novel fullerene acceptors synthesized through chemical modification for enhancing the photovoltaic performance by increasing open-circuit voltage, short-circuit current, and fill factor, which determine the performance of organic photovoltaic cells.

Synthesis of charge transfer complex of chloranilic acid as acceptor with p-nitroaniline as donor: Crystallographic, UV-visible spectrophotometric and antimicrobial studies

NASA Astrophysics Data System (ADS)

Zulkarnain; Khan, Ishaat M.; Ahmad, Afaq; Miyan, Lal; Ahmad, Musheer; Azizc, Nafe

2017-08-01

The charge transfer interaction between p-nitroaniline (PNA) and chloranilic (CAA) acid was studied spectrophotometrically in methanol at different temperatures within the range 298-328 K. This experimental work explores the nature of charge-transfer interactions that play a significant role in chemistry and biology. Structure of synthesized charge transfer (CT) complex was investigated by different technique such as X-ray crystallography, FTIR, 1HNMR, UV-visible spectroscopy, XRD and TGA-DTA, which indicates the presence of N+sbnd Hrbd2bd O- bond between donor and acceptor moieties. Spectrophotometric studies of CT complexes were carried out in methanol at different temperatures to estimate thermodynamic parameters such as formation constant (KCT), molar absorptivity (εCT), free energy change (ΔG), enthalpy change (ΔH), resonance energy (RN), oscillator strength (f), transition dipole moment (μEN) and interaction energy (ECT) were also calculated. The effect of temperatures on all the parameters was studied in methanol. 1:1 stoichiometric of CT-complex was ascertained by Benesi-Hildebrand plots giving straight line, which are good agreement with other analysis. Synthesized CT complex was screened for its antimicrobial activity such as antibacterial activity against two gram-positive bacteria, Staphylococcus aureus and bacillus subtilis and two gram negative bacteria Escherichia coli and pseudomonas aeruginosa, and antifungal activity against fungi Fusarium oxysporum, and Aspergillus flavus.

Origin of high open-circuit voltage in a planar heterojunction solar cell containing a non-fullerene acceptor

NASA Astrophysics Data System (ADS)

Cheng, Nongyi; Peng, Yuelin; Andrew, Trisha L.

2017-09-01

Vapor-deposited, planar heterojunction organic solar cells containing a periflanthene donor and either a fullerene or non-fullerene acceptor are investigated. A high VOC of 1.16 V is observed in devices containing the non-fullerene, pyrrolo[3,4-c]pyrrole-1,4-dione, 3,6-bis(4-chlorophenyl)-2,5-dihydro acceptor, whereas analogous devices containing C60 only result in a VOC of 0.8 V. The measured band energy levels of the two different acceptors do not readily explain the observed difference. Small-perturbation transient photovoltage and transient photocurrent measurements reveal that interfacial charge recombination is comparatively slower for the non-fullerene acceptor, resulting in relatively higher Voc values.

Charge transfer complex studies between some non-steroidal anti-inflammatory drugs and π-electron acceptors

NASA Astrophysics Data System (ADS)

Duymus, Hulya; Arslan, Mustafa; Kucukislamoglu, Mustafa; Zengin, Mustafa

2006-12-01

Charge transfer (CT) complexes of some non-steroidal anti-inflammatory drugs, naproxen and etodolac which are electron donors with some π-acceptors, such as tetracyanoethylene (TCNE), 2,3-dichloro-5,6-dicyano- p-benzoquinone (DDQ), p-chloranil ( p-CHL), have been investigated spectrophotometrically in chloroform at 21 °C. The coloured products are measured spectrophotometrically at different wavelength depending on the electronic transition between donors and acceptors. Beer's law is obeyed and colours were produced in non-aqueous media. All complexes were stable at least 2 h except for etodolac with DDQ stable for 5 min. The equilibrium constants of the CT complexes were determined by the Benesi-Hildebrand equation. The thermodynamic parameters Δ H, Δ S, Δ G° were calculated by Van't Hoff equation. Stochiometries of the complexes formed between donors and acceptors were defined by the Job's method of the continuous variation and found in 1:1 complexation with donor and acceptor at the maximum absorption bands in all cases.

A STUDY COMPARING CHEMICAL PEELING USING MODIFIED JESSNER'S SOLUTION AND 15%TRICHLOROACETIC ACID VERSUS 15% TRICHLOROACETIC ACID IN THE TREATMENT OF MELASMA

PubMed Central

Safoury, Omar Soliman; Zaki, Nagla Mohamed; El Nabarawy, Eman Ahmad; Farag, Eman Abas

2009-01-01

Background: Melasma is a symmetric progressive hyperpigmentation of the facial skin that occurs in all races but has a predilection for darker skin phenotypes. Depigmenting agents, laser and chemical peeling as classic Jessner's solution, modified Jessner's solution and trichloroacetic acid have been used alone and in combination in the treatment of melasma. Objectives: The aim of the study was to compare the therapeutic effect of combined 15% Trichloroacetic acid (TCA) and modified Jessner's solution with 15% TCA on melasma. Materials and Methods: Twenty married females with melasma (epidermal type), with a mean age of 38.25 years, were included in this study. All were of skin type III or IV. Fifteen percent TCA was applied to the whole face, with the exception of the left malar area to which combined TCA 15% and modified Jessner's solution was applied. Results: Our results revealed statistically highly significant difference between MASI Score (Melasma Area and Severity Index) between the right malar area and the left malar area. Conclusion: Modified Jessner's solution proved to be useful as an adjuvant treatment with TCA in the treatment of melasma, improving the results and minimizing postinflammatory hyperpigmentation. PMID:20049268

Role of Crystallization in the Morphology of Polymer: Non-fullerene Acceptor Bulk Heterojunctions

DOE PAGES

O’Hara, Kathryn A.; Ostrowski, David P.; Koldemir, Unsal; ...

2017-05-22

Many high efficiency organic photovoltaics use fullerene-based acceptors despite their high production cost, weak optical absorption in the visible range, and limited synthetic variability of electronic and optical properties. To circumvent this deficiency, non-fullerene small-molecule acceptors have been developed that have good synthetic flexibility, allowing for precise tuning of optoelectronic properties, leading to enhanced absorption of the solar spectrum and increased open-circuit voltages ( V OC). We examined the detailed morphology of bulk heterojunctions of poly(3-hexylthiophene) and the small-molecule acceptor HPI-BT to reveal structural changes that lead to improvements in the fill factor of solar cells upon thermal annealing. Themore » kinetics of the phase transformation process of HPI-BT during thermal annealing were investigated through in situ grazing incidence wide-angle X-ray scattering studies, atomic force microscopy, and transmission electron microscopy. The HPI-BT acceptor crystallizes during film formation to form micron-sized domains embedded within the film center and a donor rich capping layer at the cathode interface reducing efficient charge extraction. Thermal annealing changes the surface composition and improves charge extraction. In conclusion, this study reveals the need for complementary methods to investigate the morphology of BHJs.« less

Role of Crystallization in the Morphology of Polymer: Non-fullerene Acceptor Bulk Heterojunctions

DOE Office of Scientific and Technical Information (OSTI.GOV)

O’Hara, Kathryn A.; Ostrowski, David P.; Koldemir, Unsal

Many high efficiency organic photovoltaics use fullerene-based acceptors despite their high production cost, weak optical absorption in the visible range, and limited synthetic variability of electronic and optical properties. To circumvent this deficiency, non-fullerene small-molecule acceptors have been developed that have good synthetic flexibility, allowing for precise tuning of optoelectronic properties, leading to enhanced absorption of the solar spectrum and increased open-circuit voltages ( V OC). We examined the detailed morphology of bulk heterojunctions of poly(3-hexylthiophene) and the small-molecule acceptor HPI-BT to reveal structural changes that lead to improvements in the fill factor of solar cells upon thermal annealing. Themore » kinetics of the phase transformation process of HPI-BT during thermal annealing were investigated through in situ grazing incidence wide-angle X-ray scattering studies, atomic force microscopy, and transmission electron microscopy. The HPI-BT acceptor crystallizes during film formation to form micron-sized domains embedded within the film center and a donor rich capping layer at the cathode interface reducing efficient charge extraction. Thermal annealing changes the surface composition and improves charge extraction. In conclusion, this study reveals the need for complementary methods to investigate the morphology of BHJs.« less

Systems solutions by lactic acid bacteria: from paradigms to practice

PubMed Central

2011-01-01

Lactic acid bacteria are among the powerhouses of the food industry, colonize the surfaces of plants and animals, and contribute to our health and well-being. The genomic characterization of LAB has rocketed and presently over 100 complete or nearly complete genomes are available, many of which serve as scientific paradigms. Moreover, functional and comparative metagenomic studies are taking off and provide a wealth of insight in the activity of lactic acid bacteria used in a variety of applications, ranging from starters in complex fermentations to their marketing as probiotics. In this new era of high throughput analysis, biology has become big science. Hence, there is a need to systematically store the generated information, apply this in an intelligent way, and provide modalities for constructing self-learning systems that can be used for future improvements. This review addresses these systems solutions with a state of the art overview of the present paradigms that relate to the use of lactic acid bacteria in industrial applications. Moreover, an outlook is presented of the future developments that include the transition into practice as well as the use of lactic acid bacteria in synthetic biology and other next generation applications. PMID:21995776

Electrolyte diodes with weak acids and bases. I. Theory and an approximate analytical solution.

PubMed

Iván, Kristóf; Simon, Péter L; Wittmann, Mária; Noszticzius, Zoltán

2005-10-22

Until now acid-base diodes and transistors applied strong mineral acids and bases exclusively. In this work properties of electrolyte diodes with weak electrolytes are studied and compared with those of diodes with strong ones to show the advantages of weak acids and bases in these applications. The theoretical model is a one dimensional piece of gel containing fixed ionizable groups and connecting reservoirs of an acid and a base. The electric current flowing through the gel is measured as a function of the applied voltage. The steady-state current-voltage characteristic (CVC) of such a gel looks like that of a diode under these conditions. Results of our theoretical, numerical, and experimental investigations are reported in two parts. In this first, theoretical part governing equations necessary to calculate the steady-state CVC of a reverse-biased electrolyte diode are presented together with an approximate analytical solution of this reaction-diffusion-ionic migration problem. The applied approximations are quasielectroneutrality and quasiequilibrium. It is shown that the gel can be divided into an alkaline and an acidic zone separated by a middle weakly acidic region. As a further approximation it is assumed that the ionization of the fixed acidic groups is complete in the alkaline zone and that it is completely suppressed in the acidic one. The general solution given here describes the CVC and the potential and ionic concentration profiles of diodes applying either strong or weak electrolytes. It is proven that previous formulas valid for a strong acid-strong base diode can be regarded as a special case of the more general formulas presented here.

Alteration of chemical behavior of L-ascorbic acid in combination with nickel sulfate at different pH solutions in vitro

PubMed Central

Maniyar, Shaheen A; Jargar, Jameel G; Das, Swastika N; Dhundasi, Salim A; Das, Kusal K

2012-01-01

Objective To evaluate the alteration of chemical behavior of L-ascorbic acid (vitamin C) with metal ion (nickel) at different pH solutions in vitro. Methods Spectra of pure aqueous solution of L-ascorbic acid (E mark) compound and NiSO4 (H2O) (sigma USA) were evaluated by UV visible spectrophotometer. Spectral analysis of L-ascorbic acid and nickel at various pH (2.0, 7.0, 7.4 and 8.6) at room temperature of 29 °C was recorded. In this special analysis, combined solution of L-ascorbic acid and nickel sulfate at different pH was also recorded. Results The result revealed that λmax (peak wavelength of spectra) of L-ascorbic acid at pH 2.0 was 289.0 nm whereas at neutral pH 7.0, λmax was 295.4 nm. In alkaline pH 8.6, λmax was 295.4 nm and at pH 7.4 the λmax of L-ascorbic acid remained the same as 295.4 nm. Nickel solution at acidic pH 2.0 was 394.5 nm, whereas at neutral pH 7.0 and pH 7.4 were the same as 394.5 nm. But at alkaline pH 8.6, λmax value of nickel sulfate became 392.0 nm. The combined solution of L-ascorbic acid and nickel sulfate (6 mg/mL each) at pH 2.0 showed 292.5 nm and 392.5 nm, respectively whereas at pH 7.0, L-ascorbic acid showed 296.5 nm and nickel sulfate showed 391.5 nm. At pH 7.4, L-ascorbic acid showed 297.0 nm and nickel sulfate showed 394.0 nm in the combined solution whereas at pH 8.6 (alkaline) L-ascorbic acid and nickel sulfate were showing 297.0 and 393.5 nm, respectively. Conclusions Results clearly indicate an altered chemical behavior of L-ascorbic acid either alone or in combination with nickel sulfate in vitro at different pH. Perhaps oxidation of L-ascorbic acid to L-dehydro ascorbic acid via the free radical (HSc*) generation from the reaction of H2ASc + Ni (II) is the cause of such alteration of λmax value of L-ascorbic acid in the presence of metal nickel. PMID:23569901

Investigation of energy transfer between semiconducting polymer dot donors and hydrophilic and hydrophobic Cy5 acceptors

NASA Astrophysics Data System (ADS)

Lix, Kelsi; Algar, W. Russ

2016-09-01

Semiconducting polymer dots (Pdots) are rapidly emerging fluorescent probes for bioanalysis. Pdots have extraordinarily strong absorption and bright emission compared to other commonly used fluorescent probes, making them very attractive for applications involving Förster resonance energy transfer (FRET). Here, we investigated two FRET systems with green-emitting poly(9,9-dioctylfluorene-alt-benzothiadiazole) (F8BT) Pdots as donors and two different Cyanine 5 (Cy5) dyes as acceptors. A hydrophilic sulfo-Cy5 dye was directly conjugated to the Pdot surface using carbodiimide chemistry, and a hydrophobic Cy5 dye was observed to spontaneously partition into the core of the Pdot. FRET was observed to depend on the acceptor dye concentration with both systems, and was characterized using a combination of fluorescence emission spectra, excitation spectra, and lifetime measurements. Much stronger quenching of Pdot emission and FRET-sensitized acceptor dye emission were observed for the hydrophobic Cy5 system, and these trends were attributed to reduced donor-acceptor distances in comparison to the hydrophilic sulfo-Cy5 system. Current limitations in the experimental format are discussed. The results show that Pdots are effective FRET donors for acceptor dyes located both within and at the surface of Pdots.

Enhanced Efficiency in Fullerene-Free Polymer Solar Cell by Incorporating Fine-designed Donor and Acceptor Materials.

PubMed

Ye, Long; Sun, Kai; Jiang, Wei; Zhang, Shaoqing; Zhao, Wenchao; Yao, Huifeng; Wang, Zhaohui; Hou, Jianhui

2015-05-06

Among the diverse nonfullerene acceptors, perylene bisimides (PBIs) have been attracting much attention due to their excellent electron mobility and tunable molecular and electronic properties by simply engineering the bay and head linkages. Herein, guided by two efficient small molecular acceptors, we designed, synthesized, and characterized a new nonfullerene small molecule PPDI with fine-tailored alkyl chains. Notably, a certificated PCE of 5.40% is realized in a simple structured fullerene-free polymer solar cell comprising PPDI as the electron acceptor and a fine-tailored 2D-conjugated polymer PBDT-TS1 as the electron donor. Moreover, the device behavior, morphological feature, and origin of high efficiency in PBDT-TS1/PPDI-based fullerene-free PSC were investigated. The synchronous selection and design of donor and acceptor materials reported here offer a feasible strategy for realizing highly efficient fullerene-free organic photovoltaics.

Stepwise Bay Annulation of Indigo for the Synthesis of Desymmetrized Electron Acceptors and Donor–Acceptor Constructs

DOE PAGES

Kolaczkowski, Matthew A.; He, Bo; Liu, Yi

2016-10-10

In this work, a selective stepwise annulation of indigo has been demonstrated as a means of providing both monoannulated and differentially double-annulated indigo derivatives. Disparate substitution of the electron accepting bay-annulated indigo system allows for fine control over both the electronic properties as well as donor-acceptor structural architectures. Optical and electronic properties were characterized computationally as well as through UV-vis absorption spectroscopy and cyclic voltammetry. Finally, this straightforward method provides a modular approach for the design of indigo-based materials with tailored optoelectronic properties.

Influence of Concentration and Agitation of Sodium Hypochlorite and Peracetic Acid Solutions on Tissue Dissolution.

PubMed

Tanomaru-Filho, Mário; Silveira, Bruna Ramos Franco; Martelo, Roberta Bosso; Guerreiro-Tanomaru, Juliane Maria

2015-11-01

To evaluated the tissue dissolution of sodium hypochlorite (NaOCl) and peracetic acid (PA) solutions at different concentrations, with or without ultrasonic agitation. The following solutions were analyzed: 2.5% NaOCl, 0.5, 1 and 2% PA, 1% PA associated with 6.5% hydrogen peroxide (HP) and saline. Fragments of bovine pulp tissue with 25 ± 2g mg were immersed into test tubes containing 4 mL of the solutions for 10 minutes. In the groups with agitation, pulp tissues were submitted to 2 cycles of 1 minute of ultrasonic agitation. The specimens were weighed after the removal from the solutions. The percentage of mass loss was calculated according to the difference of mass before and after exposure to solutions. Data were submitted to ANOVA and Tukey tests (p < 0.05). A total of 2.5% NaOCl with or without agitation showed the higher tissue dissolution (between 64.5 and 67% of mass reduction) (p < 0.005). By comparing the PA solutions, the concentrations of 1 and 2% with or without agitation and the concentration of 0.5% with agitation showed similar dissolution activity (between 35.4 and 44% of mass reduction). The use of the ultrasonic agitation promoted an increase of the dissolution ability only for 0.5% PA. Peracetic acid solution has pulp tissue dissolution. However, this ability is lower than 2.5% NaOCl solution. The sodium hypochlorite solution shows higher ability to dissolve tissue than PA.