Matching Items (5)
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- All Subjects: Physical Chemistry
- All Subjects: Quinone
- Creators: Moore, Ana
- Creators: Gould, Ian R
Description
Mitochondria produce most of the ATP needed for the cell as an energy source. It is well known that cellular respiration results in oxidative damage to the cell due to the production of reactive oxygen species (ROS). Mitochondrial dysfunction is believed to contribute to a number of degenerative diseases; because of this the mitochondrial respiratory chain is considered as potential drug target. A few series of idebenone analogues with quinone, pyridinol and pyrimidinol redox cores have been synthesized and evaluated as antioxidants able to protect cellular integrity and, more specifically, mitochondrial function. The compounds exhibited a range of activities. The activities observed were used for the design of analogues with enhanced properties as antioxidants. Compounds were identified which provide better protection against oxidative stress than idebenone, and it is thought that they do so catalytically.
ContributorsArce Amezquita, Pablo M (Author) / Hecht, Sidney M. (Thesis advisor) / Moore, Ana (Committee member) / Rose, Seth (Committee member) / Arizona State University (Publisher)
Created2012
Description
This thesis focused on physicochemical and electrochemical projects directed towards two electrolyte types: 1) class of ionic liquids serving as electrolytes in the catholyte for alkali-metal ion conduction in batteries and 2) gel membrane for proton conduction in fuel cells; where overall aims were encouraged by the U.S. Department of Energy.
Large-scale, sodium-ion batteries are seen as global solutions to providing undisrupted electricity from sustainable, but power-fluctuating, energy production in the near future. Foreseen ideal advantages are lower cost without sacrifice of desired high-energy densities relative to present lithium-ion and lead-acid battery systems. Na/NiCl2 (ZEBRA) and Na/S battery chemistries, suffer from high operation temperature (>300ºC) and safety concerns following major fires consequent of fuel mixing after cell-separator rupturing. Initial interest was utilizing low-melting organic ionic liquid, [EMI+][AlCl4-], with well-known molten salt, NaAlCl4, to create a low-to-moderate operating temperature version of ZEBRA batteries; which have been subject of prior sodium battery research spanning decades. Isothermal conductivities of these electrolytes revealed a fundamental kinetic problem arisen from "alkali cation-trapping effect" yet relived by heat-ramping >140ºC.
Battery testing based on [EMI+][FeCl4-] with NaAlCl4 functioned exceptional (range 150-180ºC) at an impressive energy efficiency >96%. Newly prepared inorganic ionic liquid, [PBr4+][Al2Br7-]:NaAl2Br7, melted at 94ºC. NaAl2Br7 exhibited super-ionic conductivity 10-1.75 Scm-1 at 62ºC ensued by solid-state rotator phase transition. Also improved thermal stability when tested to 265ºC and less expensive chemical synthesis. [PBr4+][Al2Br7-] demonstrated remarkable, ionic decoupling in the liquid-state due to incomplete bromide-ion transfer depicted in NMR measurements.
Fuel cells are electrochemical devices generating electrical energy reacting hydrogen/oxygen gases producing water vapor. Principle advantage is high-energy efficiency of up to 70% in contrast to an internal combustion engine <40%. Nafion-based fuel cells are prone to carbon monoxide catalytic poisoning and polymer membrane degradation unless heavily hydrated under cell-pressurization. This novel "SiPOH" solid-electrolytic gel (originally liquid-state) operated in the fuel cell at 121oC yielding current and power densities high as 731mAcm-2 and 345mWcm-2, respectively. Enhanced proton conduction significantly increased H2 fuel efficiency to 89.7% utilizing only 3.1mlmin-1 under dry, unpressurized testing conditions. All these energy devices aforementioned evidently have future promise; therefore in early developmental stages.
Large-scale, sodium-ion batteries are seen as global solutions to providing undisrupted electricity from sustainable, but power-fluctuating, energy production in the near future. Foreseen ideal advantages are lower cost without sacrifice of desired high-energy densities relative to present lithium-ion and lead-acid battery systems. Na/NiCl2 (ZEBRA) and Na/S battery chemistries, suffer from high operation temperature (>300ºC) and safety concerns following major fires consequent of fuel mixing after cell-separator rupturing. Initial interest was utilizing low-melting organic ionic liquid, [EMI+][AlCl4-], with well-known molten salt, NaAlCl4, to create a low-to-moderate operating temperature version of ZEBRA batteries; which have been subject of prior sodium battery research spanning decades. Isothermal conductivities of these electrolytes revealed a fundamental kinetic problem arisen from "alkali cation-trapping effect" yet relived by heat-ramping >140ºC.
Battery testing based on [EMI+][FeCl4-] with NaAlCl4 functioned exceptional (range 150-180ºC) at an impressive energy efficiency >96%. Newly prepared inorganic ionic liquid, [PBr4+][Al2Br7-]:NaAl2Br7, melted at 94ºC. NaAl2Br7 exhibited super-ionic conductivity 10-1.75 Scm-1 at 62ºC ensued by solid-state rotator phase transition. Also improved thermal stability when tested to 265ºC and less expensive chemical synthesis. [PBr4+][Al2Br7-] demonstrated remarkable, ionic decoupling in the liquid-state due to incomplete bromide-ion transfer depicted in NMR measurements.
Fuel cells are electrochemical devices generating electrical energy reacting hydrogen/oxygen gases producing water vapor. Principle advantage is high-energy efficiency of up to 70% in contrast to an internal combustion engine <40%. Nafion-based fuel cells are prone to carbon monoxide catalytic poisoning and polymer membrane degradation unless heavily hydrated under cell-pressurization. This novel "SiPOH" solid-electrolytic gel (originally liquid-state) operated in the fuel cell at 121oC yielding current and power densities high as 731mAcm-2 and 345mWcm-2, respectively. Enhanced proton conduction significantly increased H2 fuel efficiency to 89.7% utilizing only 3.1mlmin-1 under dry, unpressurized testing conditions. All these energy devices aforementioned evidently have future promise; therefore in early developmental stages.
ContributorsTucker, Telpriore G (Author) / Angell, Charles A. (Committee member) / Moore, Ana (Committee member) / Seo, Dong-Kyun (Committee member) / Arizona State University (Publisher)
Created2014
Description
This dissertation describes the work on two projects which involves measuring molecular conductance and studying their properties on the nanoscale using various Scanning Tunneling Microscopy (STM) techniques. The first molecule studied was a porphyrin-fullerene moiety known as a molecular Dyad for photovoltaic applications. This project is further divided into two section, the first one involving the characterization of the Dyad monolayers and conductance measurement in the dark. The Dyads are designed to form charge separated states on illumination. The lifetime of the charged states have been measured efficiently but the single-molecule conductance through the molecules have yet to be characterized. The second part of the project describes the set-up of a novel sample stage which enables the study of molecular conductance under illumination. This part also describes the subsequent study of the molecule under illumination and the observation of a unique charge-separated state. It also contains the verification of the presence of this charge-separated using other characterization techniques like transient absorption spectroscopy. The second project described in the dissertation was studying and comparing the predicted rectifying nature of two molecules, identical in every way except for one stereocenter. This project describes the formation of monolayers of the molecule on gold and then studying and analyzing the current-voltage characteristics of the molecules and looking for rectification. Both the molecules proved to be rectifying, one more than the other as predicted by theoretical calculations.
ContributorsBhattacharyya, Shreya (Author) / Lindsay, Stuart (Thesis advisor) / Moore, Ana (Committee member) / Levitus, Marcia (Committee member) / Arizona State University (Publisher)
Created2011
Description
The field of Ionic Liquid (IL) research has received considerable attention during the past decade. Unique physicochemical properties of these low melting salts have made them very promising for applications in a many areas of science and technology such as electrolyte research, green chemistry and electrodeposition. One of the most important parameters dictating their physicochemical behavior is the basicity of their anion. Using four sets of Protic Ionic Liquids (PILs) and spectroscopic characterization of them, a qualitative order for anion basicity of ILs is obtained.
Protic Ionic Liquids are made by proton transfer form a Brønsted acid to a base. The extent of this transfer is determined by the free energy change of the proton transfer process. For the cases with large enough free energy change during the process, the result is a fully ionic material whereas if the proton transfer is not complete, a mixture of ions, neutral molecules and aggregates is resulted. NMR and IR spectroscopies along with electrochemical and mechanical characterization of four sets of PILs are used to study the degree of ionicity.
Protic Ionic Liquids are made by proton transfer form a Brønsted acid to a base. The extent of this transfer is determined by the free energy change of the proton transfer process. For the cases with large enough free energy change during the process, the result is a fully ionic material whereas if the proton transfer is not complete, a mixture of ions, neutral molecules and aggregates is resulted. NMR and IR spectroscopies along with electrochemical and mechanical characterization of four sets of PILs are used to study the degree of ionicity.
ContributorsHasani, Mohammad (Author) / Angell, C. Austen (Thesis advisor) / Yarger, Jeffrey L (Committee member) / Gould, Ian R (Committee member) / Arizona State University (Publisher)
Created2016
Description
Many natural and synthetic quinones have shown biological and pharmacological activity. Some of them have also shown anticancer activity. Ubiquinone (CoQ10) which is a natural quinone, is a component of the electron transport chain and participates in generation of ATP (adenosine triphosphate). Cellular oxidative stress is key feature of many neurodegenerative diseases such as Friedreich's ataxia, Alzheimer's disease and Parkinson's disease. The increased generation of reactive oxygen species damages cell membranes and leads to cell death. Analogues of ubiquinone in the form of pyrimidinols and pyridinols, were effective in protecting Friedreich's ataxia lymphocytes from oxidative stress- induced cell death. There were some structural features which could be identified that should be useful for the design of the analogues for cellular protection against oxidative stress. There are quinones such as doxorubicin, daunomycin and topopyrones which have anticancer activity. Here I evaluated topopyrone analogues which poison both topoisomerases I and II. The topopyrone analogues were lethal to human breast cancer cells, but these analogues were not as potent as camptothecin.
ContributorsRaghav, Nidhi (Author) / Hecht, Sidney M. (Thesis advisor) / Gould, Ian R (Committee member) / Williams, Peter (Committee member) / Arizona State University (Publisher)
Created2011