Type Of Electron Acceptor Research Articles

Electrical bistability of organic devices with a polymeric thin film for nonvolatile data storage

In this study, organic memory devices with a single active layer between the two external electrodes were fabricated using an electron-donor type conjugated polymer and an electron-acceptor type small organic molecule. The active layer of the memory device was prepared by blending polystyrene, poly[10-(2′-ethylhexyl)phenothiazine-3,7-diyl], and tetracyanoquinodimethane in 1,2-dichlorobenzene. The device initially showed a low-conductance state (OFF state) in the low-voltage range, and an abrupt current increase, corresponding to the transition to a high-conductance state (ON state), occurred at a certain voltage (Vth). The ON state could be reverted to the OFF state by applying a voltage higher than Vth. The current ratio between the two states was about 103 (up to 105). After this transition, the device remained in the ON state even after the applied voltage was removed, and this indicated the nonvolatile characteristics of the device. There was no sharp current degradation in the OFF or ON states for 4500 s of continuous bias. The device-to-device performance fluctuation was measured, and the conduction mechanisms in the ON and OFF states were examined by fitting the data to well-known theoretical models. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012

Slurry bioreactors with simultaneous electron acceptors for bioremediation of an agricultural soil polluted with lindane

The purpose of our study was 2-fold: (i) to evaluate the effect of dominant electron acceptor [either aerobic, methanogenic, or sulfate-reducing slurry bioreactor (SB)] and biostimulation with sucrose on lindane removal from heavy soil and (ii) to assess the effect of the type of combined environments [partially aerated methanogenic (PAM) and simultaneous methanogenic-sulfate reducing (M-SR)] and addition of silicone oil as solvent on lindane removal from a clayish agricultural soil with high levels of organic matter.In the first experiment, the main effect of electron acceptor was significant (p<0.0001); lindane removals followed the order SR>A≫M SBs. On the other hand, co-substrate sucrose was not significant (p=0.67). Yet, the interaction was moderately significant (p<0.007); co-substrate influence was distinct depending on the type of electron acceptor. In our case, co-substrate slightly improved lindane removal in both anoxic SBs (SR and M units), whereas lindane removal in A-SB with sucrose was lower than A-SB without sucrose. Metabolites from lindane transformation in our single electron acceptor SBs were consistent with lindane metabolites reported in the literature for anaerobic and aerobic degradation of the insecticide.In the second experiment, both factors [simultaneous electron acceptor (SEA) combination and solvent addition] were significant (p<0.0001). Removal of lindane in SEA-SBs, PAM and M-SR without silicone oil was low (∼16%). On the other hand, the order of lindane removals in SBs with oil silicone M-SR SB was significantly superior (65%) to that of PAM SB (39%).Finally, in our work, SBs with SEA where one of the anaerobic metabolites is methanogenic were not as successful as SBs with single electron acceptors for removal of lindane from heavy soil.

Synthesis and Properties of Terthiophene and Bithiophene Derivatives Functionalized by BF2 Chelation: A New Type of Electron Acceptor Based on Quadrupolar Structures

Terthiophene and bithiophene derivatives functionalized by BF(2) chelation were synthesized as a new type of electron acceptor, and their properties were compared to those of bifuran and biphenyl derivatives. These new compounds are characterized by quadrupolar structures due to resonance contributors generated by BF(2) chelation. The bithiophene derivative has a strong quadrupolar character compared with the bifuran and biphenyl derivatives because their hydrolytic analyses indicated that the bithiophene moiety has a larger on-site Coulomb repulsion than the others. The terthiophene derivative has a smaller on-site Coulomb repulsion than the bithiophene derivative due to the addition of a thiophene spacer. These BF(2) complexes exhibit long-wavelength absorptions and according to measurements of ionization potentials and absorption edges they have energetically low-lying HOMOs and LUMOs. The crystal structure of the bithiophene derivative is of the herringbone type, with short F···S and F···C contacts affording dense crystal packing. n-Type semiconducting behaviour was observed in organic field-effect transistors based on these BF(2) complexes.

Effect of different types of electron acceptors on the anoxic phosphorus uptake activity of denitrifying phosphorus removing bacteria

The effect of different types of electron acceptors (O 2, NO 3 - and NO 2 - ) on anoxic phosphorus uptake was investigated to obtain a better understanding of the metabolic behavior of denitrifying phosphorus removing bacteria (DPB). Two sets of sequencing batch reactor (SBR) were used to enrich phosphorus accumulation organisms (PAOs) by alternative anaerobic and aerobic operations (oxygen was used as the electron acceptor), batch experiments under two different electron acceptor conditions, nitrate and nitrite, were performed by using activated sludge generated from the above-operated SBR reactors. Anoxic phosphorus uptake achieved successful both by using nitrate or nitrite as the electron acceptor. However, the relative small amount of anoxic phosphorus was taken up by microorganisms with nitrite used as the electron acceptor in comparison with nitrate. The optimal stoichiometric loading amount of electron acceptors of nitrate and nitrite to phosphorus (N/P ratio) were 0.89 and 0.60, respectively. If the initial concentration of electron acceptors was controlled below the optimal ratio, the amount of phosphorus taken up increased with the concentration, otherwise it would decrease. It was also found that DPB lost the ability of phosphorus release and uptake rapidly under continuous anaerobic–anoxic operation condition.

Synthesis, Crystal Structure, and Electron-Accepting Property of the BF2 Complex of a Dihydroxydione with a Perfluorotetracene Skeleton

A BF(2) complex containing an octafluorotetracene moiety was synthesized as a new type of electron acceptor. This compound exhibits a long-wavelength absorption based on the perfluorotetracene skeleton and high electron affinity due to its quadrupolar structure enhanced by fluorination. In the crystal, the molecules are arranged with short F...pi and F...F contacts affording a dense crystal packing. The BF(2) complex exhibited n-type semiconducting behavior.

Molecular Design of Organic Dyes with Double Electron Acceptor for Dye-Sensitized Solar Cell

We designed and synthesized novel organic dyes of double electron acceptor type based on phenothiazine framework, as photosensitizers for the dye-sensitized solar cell (DSC). The density functional theory (DFT) and time-dependent density functional theory (TD-DFT) calculations were used to estimate the photovoltaic properties of the dyes in the design stage. The molecular structure having two electron acceptors on both sides of phenothiazine moiety provided the efficient electron extraction paths from electron donor part, which was demonstrated by the analysis of the electronic structures on donor and acceptor, and the excitations between HOMOs and LUMOs. In accordance, the measurements of photovoltaic properties of the DSCs prepared in the laboratory scale showed that the organic dyes of double electron acceptor type gave about 20% higher performace than their counterparts of single electron acceptor type. The effect of the kind of electron acceptor (C, cyanocrylic acid and R, rhodanine-acetic acid) on the performance of DSC was studied as well. We found that the organic dyes with R as acceptor gave much lower efficiencies, compared to those with C, for both single and double electron acceptor type. It was attributed to the electronic decoupling between anchoring and TiO2 conduction band accompanying the lack of π-conjugation of carboxylic group as anchoring on R, despite that the dyes with R had relatively broad and intense absorption spectra in the visible region.

Near‐Infrared Emission Quantum Yield of Soluble Short Single‐Walled Carbon Nanotubes

Soluble short single-walled carbon nanotubes in aerated D(2)O emit in the near-infrared (NIR) region [picture: see text] with a quantum yield of (3.9+/-0.5) x10(-3) and a half-life of 7.65 micros. This emission is quenched by electron- acceptor molecules. Soluble short single-walled carbon nanotubes (sSWNT) are prepared by means of chemical fragmentation and purification of commercial SWNTs. The average length of the nanotubes, as estimated by microscopy, is 400 nm. Infrared spectroscopy studies reveal the presence of a significant population of carboxyl groups. The thermogravimetric profile of an sSWNT shows that this material is hydrophilic, contains carboxyl groups, and is almost free from inorganic impurities. In D(2)O solution, the obtained sSWNTs emit in the near-infrared (NIR) region with a quantum yield of (3.9+/-0.5)x10(-3), determined using the 1270 nm singlet oxygen emission as a reference standard. The temporal profile can be fitted with first-order kinetics and a half-life of 13.9 micros. The NIR emission is quenched through a static mechanism by 2,4,6-triphenylpyrylium (TP(+)), a typical electron acceptor.

Synthesis, mesomorphism and electronic properties of nonaflate and cyano-substituted pentyloxy and 3-methylbutyloxy triphenylenes

Despite recent advances in the application of discotic liquid crystals (DLC) in organic electronic devices a better understanding of structure–property relationships is required for designing commercially viable discotic semiconductors. This is a complex task because a single structural change to the DLC may affect many relevant properties of the discotic material such as chemical stability, mesomorphism, alignment, and electronic properties. Presented here is a comprehensive study of hexa-substituted triphenylene derivatives containing pentyloxy and 3-methylbutyloxy groups as well as one or three nonaflate or cyano groups. The compounds are synthesized by both established and new synthetic approaches and are isolated as pure isomers. Their structure–mesomorphism relationship is studied by optical polarized microscopy, thermal analysis, and variable temperature X-ray diffraction and their relationships between structure and frontier orbital energies are investigated by cyclic voltammetry in solution, UV-Vis spectroscopy and computational studies at the DFT level. Both mesomorphism and frontier orbital energies of the compounds depend on the number and positions of nonaflate and cyano groups while only their mesomorphism is affected by a change from linear pentyloxy to branched 3-methylbutyloxy chains. To our surprise lowering the symmetry of the compounds is equally effective in lowering HOMO–LUMO gaps than the attachment of strongly π-electron withdrawing cyano groups. Consequently, the non-symmetrically substituted triphenylenes with three cyano groups are the most electron deficient and have the smallest HOMO–LUMO gap of the compounds prepared here but their ELUMO of about −2.8 eV is still high in comparison to typical electron acceptors (ELUMO below −3.5 eV). The computational approach established for the prepared compounds is also employed for the prediction of frontier orbital energies of new electron deficient discotic triphenylene derivatives.

Synthesis and Properties of BF2 Complexes to Dihydroxydiones of Tetracene and Perylene: Novel Electron Acceptors Showing n-Type Semiconducting Behavior

BF(2) complexes containing tetracene and perylene moieties were synthesized as new types of electron-deficient arene compounds. These compounds exhibit long wavelength absorption and high electron affinities, as revealed through spectral and electrochemical studies, due to their quadrupolar structures represented by resonance contributors. The BF(2) complex containing tetracene exhibits an n-type semiconducting behavior. These compounds are new types of electron acceptors functionalized by BF(2) chelation.

A microbial fuel cell using permanganate as the cathodic electron acceptor

The microbial fuel cell (MFC) was proved to be a novel bioprocess capable of recovering electrical energy from organic matter. In this study, we report that by using permanganate as the cathodic electron acceptor for a MFC we were actually able to recover much more electrical power than using other existing types of electron acceptors, e.g. using permanganate as the cathodic electron acceptor for a two-chamber MFC generated a maximum power density of 115.60 mW m −2 which was, respectively, 4.5- and 11.3-fold higher than that produced by using hexacynoferrate (25.62 mW m −2) and oxygen (10.2 mW m −2) as the cathodic electron acceptor. This could be attributed to the higher open circuit potential (OCP) provided by permanganate in the MFC. Besides, pH, unlike permanganate concentration, was further found to have a major impact on the OCP and the cathode potential. SEM and XPS analysis demonstrated that manganese dioxide (MnO 2) was in fact the main reduced product of the permanganate at pH 3.6. Moreover, as compared to a two-chamber MFC, a bushing MFC using permanganate as the cathodic electron acceptor achieved an unprecedented maximum power-output of 3986.72 mW m −2. This study for the first time showed that permanganate could be used as an effective cathodic electron acceptor for a MFC.

Kinetic and chemical analyses of the cytokinin dehydrogenase-catalysed reaction: correlations with the crystal structure.

CKX (cytokinin dehydrogenase) is a flavoprotein that cleaves cytokinins to adenine and the corresponding side-chain aldehyde using a quinone-type electron acceptor. In the present study, reactions of maize (Zea mays) CKX with five different substrates (N6-isopentenyladenine, trans-zeatin, kinetin, p-topolin and N-methyl-isopentenyladenine) were studied. By using stopped-flow analysis of the reductive half-reaction, spectral intermediates were observed indicative of the transient formation of a binary enzyme-product complex between the cytokinin imine and the reduced enzyme. The reduction rate was high for isoprenoid cytokinins that showed formation of a charge-transfer complex of reduced enzyme with bound cytokinin imine. For the other cytokinins, flavin reduction was slow and no charge-transfer intermediates were observed. The binary complex of reduced enzyme and imine product intermediate decays relatively slowly to form an unbound product, cytokinin imine, which accumulates in the reaction mixture. The imine product only very slowly hydrolyses to adenine and an aldehyde derived from the cytokinin N6 side-chain. Mixing of the substrate-reduced enzyme with Cu2+/imidazole as an electron acceptor to monitor the oxidative half-reaction revealed a high rate of electron transfer for this type of electron acceptor when using N6-isopentenyladenine. The stability of the cytokinin imine products allowed their fragmentation analysis and structure assessment by Q-TOF (quadrupole-time-of-flight) MS/MS. Correlations of the kinetic data with the known crystal structure are discussed for reactions with different cytokinins.

Evaluating factors that influence microbial phenanthrene biodegradation rates by regression with categorical variables

To advance the accuracy of bioremediation measurements, it is useful before specific experiments to attribute or estimate the influence of both experimental as well as field conditions on the expected magnitudes of microbial degradation rate coefficients. This paper analyzes the numerical contribution, or influence, of categories of conditions, such as bacterial adaptive state, electron acceptor type, mixing, generalized sorption conditions, and biodegradation temperature, on published phenanthrene biodegradation rates as an example of our regression approach. A fundamental microbial degradation rate equation is transformed to an additive model, then using multiple linear regression on published data, coefficients (of categorical variables) and a linear model are presented that estimate first-order biodegradation rate coefficients to within a factor of 3. Numerical estimates of how much bacterial adaptive state and presence of a sorption phase, the two most statistically significant factors, alter the phenanthrene biodegradation rate are presented. The influence of some measurement or field conditions, for example, the influence of oxygen reduction versus optimal nitrate reduction, cannot be distinguished statistically given the available data and range. The regression model is tested using conditions from newly published papers to estimate a priori the expected rate, which compares very favorably to measurements reported in the papers. Due to limited published data and range for extreme cases, the current coefficients do not apply to degradation of very aged phenanthrene nor very low concentrations of electron acceptors. As estimating tools, however, the coefficients themselves and the regression approach have very beneficial roles in design of experiments for both laboratory and field settings. Our method can be applied to other PAHs as sufficient data become available.

A new method for characterizing denitrifying phosphorus removal bacteria by using three different types of electron acceptors

This study investigated the characteristics of denitrifying phosphorus removal bacteria by using three different types of electron acceptors as well as the positive role of nitrite in phosphorus removal process. Denitrifying phosphorous removal bacteria was enriched under anaerobic–anoxic (A/A) condition. To understand A/A sludge better, sludge from two other sources were also studied. These include sludges obtained from a lab-scale anaerobic–anoxic–aerobic (A/A/O) system and a local sewage treatment plant. Three types of possible electron acceptors (oxygen, nitrate and nitrite) were examined for their roles in phosphorus uptake. The results obtained indicated that oxygen, nitrate and nitrite were able to act as electron acceptors successfully. This observation suggested that in addition to the two well-accepted groups of phosphorus removal bacteria (one can only utilize oxygen to take up phosphorus, P O, while the other can use both oxygen and nitrate, P ON), a new group of phosphorus removal bacteria, P ONn, which could use oxygen, nitrate or nitrite to take up phosphorus was identified. The relative population of these three types of bacteria could be calculated from results obtainable from phosphorus uptake batch experiments with either oxygen or nitrate or nitrite as electron acceptor. The results obtained in this study showed that A/A sludge had similar phosphorus removal performance as the A/A/O sludge. However, it has better denitrifying phosphorus removal capability, which was demonstrated by the relative population of the three groups of bacteria. The results also suggested that nitrite was not an inhibitor to phosphorus removal process. Instead, it is an alternative electron acceptor to oxygen or nitrate.

The preorganization step in organic reaction mechanisms. Charge-transfer complexes as precursors to electrophilic aromatic substitutions.

Metastable (pre-reactive) intermediates, as commonplace transients in simple bimolecular reactions, are usually unobserved (and ignored)-though they provide vital mechanistic insight. Thus, the preequilibrium (charge-transfer) complexes of various aromatic donors with rather typical electron acceptors such as Br(2), NO(+), and NO(2)(+) are examined quantitatively (via their molecular and electronic structures) to reveal surprisingly unorthodox aspects of what is conventionally referred to in organic chemistry textbooks as electrophilic aromatic bromination, nitrosation, and nitration, respectively.

Characterization of denitrifying phosphate-accumulating organisms cultivated under different electron acceptor conditions using polymerase chain reaction-denaturing gradient gel electrophoresis assay

To investigate the characteristics and the microbial diversity of denitrifying phosphate-accumulating organisms (DNPAOs) that are capable of conducting enhanced biological phosphorus removal (EBPR) using nitrate as electron acceptor, three sequencing batch reactors were operated under three different electron acceptor conditions, i.e., only oxygen, oxygen together with nitrate and only nitrate. Based on the chemical analysis concerning the biochemical transformation of each reactor, it was found that phosphate-accumulating organisms responsible for EBPR consisted of at least three populations including DNPAOs, and that the microbial community structure was changed according to the electron acceptor conditions. Also, the sludge cultivated with oxygen together with nitrate showed a drastic increase in the amount of phosphorus uptake under anoxic conditions, which suggested that a proportion of DNPAOs capable of utilizing nitrate under aerobic conditions were present. On the other hand, the change in microbial community structure depending on the type of electron acceptor was demonstrated by the analysis of the results of denaturing gradient gel electrophoresis of polymerase chain reaction-amplified 16S ribosomal DNA fragments. It was found that the bacteria commonly contained in all the reactors were Rhodocyclus sp. (96% identity) and Dechlorimonas sp. (97% identity) that belonged to the beta subclass of Proteobacteria on the basis of the analysis of the sequence excised from DGGE bands and the determination of phylogenetic affiliation. However, only the presence of Rhodocyclus sp. in all the reactors was demonstrated by fluorescent in situ hybridization analysis.

Charge carrier transport in poly[methyl(phenyl)silylene]: the effect of additives

AbstractPoly[methyl(phenyl)silylene], PMPSi, was doped with compounds of the electron acceptor type. The charge carrier mobility increases with increasing electron affinity of the acceptors having zero dipole moments. At the same time the energy distribution of hopping states narrows. On the other hand, the hole drift mobility is influenced by the dipole moment of the dopand. The electrostatic charge carrier‐dipole interaction causes a broadening of the energy distribution of transport states which results in a decrease in the charge carrier mobility. The charge carrier transport can be explained by the disordered polaronic theory, according to which the activation energy of charge carrier mobility has contributions based on the dynamic disorder, i.e. the polaronic barrier, and on the static disorder, i.e. the variation of the energy of transport states as a result of the environment. Copyright © 2001 John Wiley &amp; Sons, Ltd.

Metabolic behavior of denitrifying phosphate-accumulating organisms under nitrate and nitrite electron acceptor conditions

The effects of various types of electron acceptors on anoxic phosphorus uptake were investigated in detail to obtain a better insight into the metabolic behavior of denitrifying phosphate-accumulating organisms. Batch experimental tests under three different electron acceptor conditions, i.e., nitrate, nitrite and mixtures of nitrate and nitrite, were carried out using activated sludge cultivated in a sequencing batch reactor. The experimental results confirmed no inhibition of the utilization of nitrate or nitrite as an electron acceptor for anoxic phosphorus uptake. Anoxic phosphorus uptake occurred provided there was an electron acceptor present regardless of whether it was nitrate or nitrite. However, for nitrite a relatively small amount of anoxic phosphorus was taken up per nitrogen denitrified compared to nitrate. On the other hand, the amount of anoxic phosphorus taken up per nitrogen denitrified increased with an increase in the initial loading amount of electron acceptor in the case of nitrate, whereas it slightly decreased nitrite. Moreover, the amount of phosphorus taken up per nitrogen denitrified decreased with increasing mixed liquor suspended solid (MLSS) concentration in the case of nitrate, while it slightly increased for nitrite. From these results, it was confirmed that the activity of anoxic phosphorus uptake is strongly associated with the type and the initial loading amount of electron acceptor and the MLSS concentration under anoxic conditions.

Metabolic Behavior of Denitrifying Phosphate-Accumulating Organisms under Nitrate and Nitrite Electron Acceptor Conditions.

The effects of various types of electron acceptors on anoxic phosphorus uptake were investigated in detail to obtain a better insight into the metabolic behavior of denitrifying phosphate-accumulating organisms. Batch experimental tests under three different electron acceptor conditions, i.e., nitrate, nitrite and mixtures of nitrate and nitrite, were carried out using activated sludge cultivated in a sequencing batch reactor. The experimental results confirmed no inhibition of the utilization of nitrate or nitrite as an electron acceptor for anoxic phosphorus uptake. Anoxic phosphorus uptake occurred provided there was an electron acceptor present regardless of whether it was nitrate or nitrite. However, for nitrite a relatively small amount of anoxic phosphorus was taken up per nitrogen denitrified compared to nitrate. On the other hand, the amount of anoxic phosphorus taken up per nitrogen denitrified increased with an increase in the initial loading amount of electron acceptor in the case of nitrate, whereas it slightly decreased nitrite. Moreover, the amount of phosphorus taken up per nitrogen denitrified decreased with increasing mixed liquor suspended solid (MLSS) concentration in the case of nitrate, while it slightly increased for nitrite. From these results, it was confirmed that the activity of anoxic phosphorus uptake is strongly associated with the type and the initial loading amount of electron acceptor and the MLSS concentration under anoxic conditions.

Interfacial Electron Transfer in MoS2 Nanoclusters

ABSTRACTThe dynamics of photoinduced electron transfer between 3.0 nm diameter MoS2 nanoclusters and adsorbed electron acceptors have been studied using static and time resolved optical spectroscopy. Two types of electron acceptors are adsorbed on these nanoclusters: 2,2'-bipyridine and 4,4',5,5'-tetramethyl-2,2'-bipyridine. The results reported here focus on the interpretation of the strongly non-exponential electron transfer kinetics. Electron/hole recombination kinetics have previously been analyzed in terms of a simple distributed kinetics model, and this model is extended to include the case of interfacial electron transfer.

A systematic STM study of planar aromatic molecules on inorganic substrates: I. Submolecular image contrast

High resolution images of planar aromatic molecules exhibit a characteristic intramolecular tunneling current distribution in the STM. In this study we have investigated the correlation of this image contrast with the specific chemical nature of the molecules. For weakly bonded molecules on graphite and MoS 2 the image contrast is dominated by the wavefunction of the specific frontier orbital being closest to the Fermi level of the substrate. For electron acceptor type molecules this is the lowest unoccupied molecular orbital (LUMO), whereas for electron donor type molecules the highest occupied molecular orbital (HOMO) has been observed. On the stronger binding Ag(111) surface we found acceptor type molecules showing an unchanged image contrast compared with graphite and donor type molecules where the image contrast changes from HOMO on graphite to LUMO on Ag(111).