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(1 - 12 of 12)
- Title
- An Electrochemical Approach To Measuring Oxidative Stability Of Solid Polymer Electrolytes For Lithium Batteries.
- Creator
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Hallinan, Daniel T., Rausch, Alexander, McGill, Brandon
- Abstract/Description
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Polymer electrolytes are an interesting class of electrolytes that hold promise for safer, flexible, high-energy batteries. Block copolymer electrolytes that contain polystyrene, poly(ethylene oxide) (PEO) and lithium bis-trifluoromethanesulfonimide salt (LiTFSI) are compatible with lithium metal. However, the compatibility of PEO-based electrolyte with advanced lithium positive electrodes has not been conclusively demonstrated. Therefore, oxidative stability of PEO+LiTFSI and the block...
Show morePolymer electrolytes are an interesting class of electrolytes that hold promise for safer, flexible, high-energy batteries. Block copolymer electrolytes that contain polystyrene, poly(ethylene oxide) (PEO) and lithium bis-trifluoromethanesulfonimide salt (LiTFSI) are compatible with lithium metal. However, the compatibility of PEO-based electrolyte with advanced lithium positive electrodes has not been conclusively demonstrated. Therefore, oxidative stability of PEO+LiTFSI and the block copolymer electrolyte with common current collectors and against inert working electrodes have been investigated electrochemically. The solid nature of these polymer electrolytes is a challenge for electrochemical investigations, since most electrochemical experiments have been designed for liquid electrolyte. In order to quantitatively evaluate polymer electrolyte stability, an electrochemical approach especially designed for solid electrolytes is presented. This approach uses a set of linear sweep voltammograms from different, large overpotentials to open circuit voltage, which the authors term variable reverse linear sweep voltammetry. By allowing the cell to relax between each polarization, the first data points of each voltammogram are not mass transfer limited. This yields current versus overpotential data that can be analyzed with a kinetic model, such as the Butler-Volmer model. The block copolymer electrolyte has been found to be quite stable to electrochemical oxidation, up to 5 V at 40 degrees C. The degradation reaction has been found to be slow with large thermal activation energy. (C) 2016 Elsevier Ltd. All rights reserved.
Show less - Date Issued
- 2016-11-02
- Identifier
- FSU_libsubv1_wos_000384873600005, 10.1016/j.ces.2016.06.054
- Format
- Citation
- Title
- Birnessite: A Layered Manganese Oxide to Capture Sunlight for Water-Splitting Catalysis.
- Creator
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Mendoza-Cortes, Jose L., Lucht, Kevin P.
- Abstract/Description
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We show a comprehensive study on the structure and electronic properties of a layered manganese oxide commonly known as Birnessite. We present the effects of substituting different intercalated cations (Li+, Na+, K+, Be2+, Mg2+, Ca2+, Sr2+, Zn2+, B3+, Al3+, Ga3+, Sc3+, and Y3+) and the role of waters in the intercalated layer. The importance of the Jahn-Teller effect and ordering of the Mn3+ centers due to cation intercalation are addressed to explain the ability to tune the indirect band gap...
Show moreWe show a comprehensive study on the structure and electronic properties of a layered manganese oxide commonly known as Birnessite. We present the effects of substituting different intercalated cations (Li+, Na+, K+, Be2+, Mg2+, Ca2+, Sr2+, Zn2+, B3+, Al3+, Ga3+, Sc3+, and Y3+) and the role of waters in the intercalated layer. The importance of the Jahn-Teller effect and ordering of the Mn3+ centers due to cation intercalation are addressed to explain the ability to tune the indirect band gap (Eig) from 2.63 eV to ∼2.20 eV and the direct band gap (Edg) from 3.09 eV to ∼2.50 eV. By aligning the structures’ bands, we noted that structures with Sr, Ca, B, and Al have potential for usage in water-splitting, and anhydrous B-Birnessite is predicted to have a suitable direct band gap for light capturing. Furthermore, we also demonstrate how the effects of cations in the bulk differ from the behavior on single layer surfaces. More specifically, we show that an indirect to direct band transition is observed when we separate the bulk into a single layer oxide. This study shows a new strategy for tuning the band gap of layered materials to capture light which may couple to its intrinsic water-splitting catalytic properties, thus resembling photosynthesis.
Show less - Date Issued
- 2015-09-21
- Identifier
- FSU_libsubv1_scholarship_submission_1472154701, 10.1021/acs.jpcc.5b07860
- Format
- Citation
- Title
- Coexistence of Weyl physics and planar defects in the semimetals TaP and TaAs.
- Creator
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Besara, T., Rhodes, D. A., Chen, K.-W., Das, S., Zhang, Q. R., Sun, J., Zeng, B., Xin, Y., Balicas, L., Baumbach, R. E., Manousakis, E., Singh, D. J., Siegrist, T.
- Abstract/Description
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We report a structural study of the Weyl semimetals TaAs and TaP, utilizing diffraction and imaging techniques, where we show that they contain a high density of defects, leading to nonstoichiometric single crystals of both semimetals. Despite the observed defects and nonstoichiometry on samples grown using techniques already reported in the literature, de Haas-van Alphen measurements on TaP reveal quantum oscillations and a high carrier mobility, an indication that the crystals are of...
Show moreWe report a structural study of the Weyl semimetals TaAs and TaP, utilizing diffraction and imaging techniques, where we show that they contain a high density of defects, leading to nonstoichiometric single crystals of both semimetals. Despite the observed defects and nonstoichiometry on samples grown using techniques already reported in the literature, de Haas-van Alphen measurements on TaP reveal quantum oscillations and a high carrier mobility, an indication that the crystals are of quality comparable to those reported elsewhere. Electronic structure calculations on TaAs reveal that the position of the Weyl points relative to the Fermi level shift with the introduction of vacancies and stacking faults. In the case of vacancies the Fermi surface becomes considerably altered, while the effect of stacking faults on the electronic structure is to allow the Weyl pockets to remain close to the Fermi surface. The observation of quantum oscillations in a nonstoichiometric crystal and the persistence of Weyl fermion pockets near the Fermi surface in a crystal with stacking faults point to the robustness of these quantum phenomena in these materials.
Show less - Date Issued
- 2016-06-27
- Identifier
- FSU_libsubv1_wos_000378816000007, 10.1103/PhysRevB.93.245152
- Format
- Citation
- Title
- Crystallite Dissolution In Peo-based Polymers Induced By Water Sorption.
- Creator
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Oparaji, Onyekachi, Zuo, Xiaobing, Hallinan, Daniel T.
- Abstract/Description
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Poly(styrene-block-ethylene oxide) (PS-b-PEO) is a model hierarchically nanostructured polymer that contains PEO crystallites within microphase segregated block copolymer morphology. In order to investigate dynamics in this hierarchically nanostructured polymer, water was used as a selective, interacting probe molecule. First, the equilibrium effect of water sorption on the polymer structure was examined. Then, the coupled dynamics of structural changes and water diffusion were studied. At...
Show morePoly(styrene-block-ethylene oxide) (PS-b-PEO) is a model hierarchically nanostructured polymer that contains PEO crystallites within microphase segregated block copolymer morphology. In order to investigate dynamics in this hierarchically nanostructured polymer, water was used as a selective, interacting probe molecule. First, the equilibrium effect of water sorption on the polymer structure was examined. Then, the coupled dynamics of structural changes and water diffusion were studied. At moderate water activity, crystallite dissolution caused water diffusion to appear non-Fickian (determined by Fourier Transform infrared - attenuated total reflectance spectroscopy). PEO deliquescence was so extreme at high water activity that dynamics could not be measured in a homopolymer control. In the block copolymer at unity water activity, a second stage of water sorption occurred that was attributed to relaxation of the glassy PS phase. Water desorption was ten times faster than sorption. Desorption is thought to be less hindered by tortuosity resulting from PEO crystallites. These results are of interest for a wide-range of applications including batteries and fuel cells, water desalination, food packaging, and biomedical implants. (C) 2016 Elsevier Ltd. All rights reserved.
Show less - Date Issued
- 2016-09-25
- Identifier
- FSU_libsubv1_wos_000383925800025, 10.1016/j.polymer.2016.08.026
- Format
- Citation
- Title
- Design Principles for High H2 Storage Using Chelation of Abundant Transition Metals in Covalent Organic Frameworks for 0-700 bar at 298 K.
- Creator
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Jose L Mendoza-Cortez, Mendoza-Cortez, Jose L, Yohanes Pramudya, Pramudya, Yohanes
- Abstract/Description
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Physisorption is an effective route to meet hydrogen gas (H2) storage and delivery requirements for transportation because it is fast and fully reversible under mild conditions. However, most current candidates have too small binding enthalpies to H2 which leads to volumetric capacity less than 10 g/L compared to that of the system target of 40 g/L at 298 K. Accurate quantum mechanical (QM) methods were used to determine the H2 binding enthalpy of 5 linkers which were chelated with 11...
Show morePhysisorption is an effective route to meet hydrogen gas (H2) storage and delivery requirements for transportation because it is fast and fully reversible under mild conditions. However, most current candidates have too small binding enthalpies to H2 which leads to volumetric capacity less than 10 g/L compared to that of the system target of 40 g/L at 298 K. Accurate quantum mechanical (QM) methods were used to determine the H2 binding enthalpy of 5 linkers which were chelated with 11 different transition metals (Tm), including abundant first-row Tm (Sc through Cu), totaling 60 molecular compounds with more than 4 configurations related to the different number of H2 that interact with the molecular compound. It was found that first-row Tm gave similar and sometimes superior van der Waals interactions with H2 than precious Tm. Based on these linkers, 30 new covalent organic frameworks (COFs) were constructed. The H2 uptakes of these new COFs were determined using quantum mechanics (QM)-based force fields and grand canonical Monte Carlo (GCMC) simulations. For the first time, the range for the adsorption pressure was explored for 0–700 bar and 298 K. It was determined that Co-, Ni-, and Fe-based COFs can give high H2 uptake and delivery when compared to bulk H2 on this unexplored range of pressure.
Show less - Date Issued
- 2016-10-28
- Identifier
- FSU_libsubv1_scholarship_submission_1480625626, 10.1021/jacs.6b08803
- Format
- Set of related objects
- Title
- Dirac Cone in two dimensional bilayer graphene by intercalation with V, Nb, and Ta transition metals.
- Creator
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Pakhira, Srimanta, Lucht, Kevin P., Mendoza-Cortes, Jose L.
- Abstract/Description
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Bilayer graphene (BLG) is semiconductor whose band gap and properties can be tuned by various methods such as doping or applying gate voltage. Here, we show how to tune electronic properties of BLG by intercalation of transition metal (TM) atoms between two monolayer graphene (MLG) using a novel dispersion-corrected first-principle density functional theory approach. We intercalated V, Nb, and Ta atoms between two MLG. We found that the symmetry, the spin, and the concentration of TM atoms in...
Show moreBilayer graphene (BLG) is semiconductor whose band gap and properties can be tuned by various methods such as doping or applying gate voltage. Here, we show how to tune electronic properties of BLG by intercalation of transition metal (TM) atoms between two monolayer graphene (MLG) using a novel dispersion-corrected first-principle density functional theory approach. We intercalated V, Nb, and Ta atoms between two MLG. We found that the symmetry, the spin, and the concentration of TM atoms in BLG-intercalated materials are the important parameters to control and to obtain a Dirac Cone in their band structures. Our study reveals that the BLG intercalated with one Vanadium (V) atom, BLG-1V, has a Dirac Cone at the K-point. In all the cases, the present DFT calculations show that the 2pz sub-shells of C atoms in graphene and the 3dyz sub-shells of the TM atoms provide the electron density near the Fermi level EF which controls the material properties. Thus, we show that out-of-plane atoms can influence in-plane electronic densities in BLG, and enumerate the conditions necessary to control the Dirac point. This study presents a new strategy for controlling the material properties of BLG so that they exhibit various behaviors, including: metal, semi-metal, and semiconductor by varying the concentration and spin arrangement of the TM atoms in BLG while offering insight into the physical properties of 2D BLG-intercalated materials.
Show less - Date Issued
- 2017-09-16
- Identifier
- FSU_libsubv1_scholarship_submission_1519056039_9000b4fa
- Format
- Citation
- Title
- Flow Of Viscoelastic Fluids Around A Sharp Microfluidic Bend: Role Of Wormlike Micellar Structure.
- Creator
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Hwang, Margaret Y., Mohammadigoushki, Hadi, Muller, Susan J.
- Abstract/Description
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We examine the flow and instabilities of three viscoelastic fluids-a semidilute aqueous solution of polyethylene oxide (PEO) and two wormlike micellar solutions of cetylpyridinium chloride and sodium salicylate-around a microfluidic 90. bend, in which shear deformation and streamline curvature dominate. Similar to results reported by Gulati et al. [S. Gulati et al., Phys. Rev. E 78, 036314 (2008); J. Rheol. 54, 375 (2010)] for PEO solutions, we report a criticalWeissenberg number (Wi) for the...
Show moreWe examine the flow and instabilities of three viscoelastic fluids-a semidilute aqueous solution of polyethylene oxide (PEO) and two wormlike micellar solutions of cetylpyridinium chloride and sodium salicylate-around a microfluidic 90. bend, in which shear deformation and streamline curvature dominate. Similar to results reported by Gulati et al. [S. Gulati et al., Phys. Rev. E 78, 036314 (2008); J. Rheol. 54, 375 (2010)] for PEO solutions, we report a criticalWeissenberg number (Wi) for the onset of lip vortex formation upstream of the corner. However, the decreased aspect ratio (channel depth to width) results in a slightly higher critical Wi and a vortex that grows more slowly. We consider wormlike micellar solutions of two salt to surfactant concentration ratios R = 0.55 and R = 0.79. At R = 0.55, the wormlike micelles are linear and exhibit strong viscoelastic behavior, but at R = 0.79, the wormlike micelles become branched and exhibit shear- banding behavior. Microfluidic experiments on the R = 0.55 solution reveal two flow transitions. The first transition, at Wi = 6, is characterized by the formation of a stationary lip vortex upstream of the bend; at the second transition, at Wi = 20, the vortex fluctuates in time and changes size. The R = 0.79 solution also exhibits two transitions. The first transition at Wi = 4 is characterized by the appearance of two intermittent vortices, one at the lip and one at the far outside corner. Increasing the flow rate to Wi > 160 results in a transition to a second unstable regime, where there is only a lip vortex that fluctuates in size. The difference in flow transitions in PEO and wormlike micellar solutions presumably arises from the additional contribution of wormlike micellar breakage and reformation under shear. The flow transitions in wormlike micellar solutions are also significantly affected by chain branching.
Show less - Date Issued
- 2017-04-27
- Identifier
- FSU_libsubv1_wos_000400249900002, 10.1103/PhysRevFluids.2.043303
- Format
- Citation
- Title
- Gold Nanoparticle Monolayers From Sequential Interfacial Ligand Exchange And Migration In A Three-phase System.
- Creator
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Yang, Guang, Hallinan, Daniel T.
- Abstract/Description
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Using a three-phase system, centimeter-scale monolayer gold nanoparticle (Au NP) films have been prepared that have long-range order and hydrophobic ligands. The system contains an interface between an aqueous phase containing Au NPs and an oil phase containing one of various types of amine ligands, and a water/air interface. As the Au NPs diffuse to the water/oil interface, ligand exchange takes place which temporarily traps them at the water/oil interface. The ligand-exchanged particles...
Show moreUsing a three-phase system, centimeter-scale monolayer gold nanoparticle (Au NP) films have been prepared that have long-range order and hydrophobic ligands. The system contains an interface between an aqueous phase containing Au NPs and an oil phase containing one of various types of amine ligands, and a water/air interface. As the Au NPs diffuse to the water/oil interface, ligand exchange takes place which temporarily traps them at the water/oil interface. The ligand-exchanged particles then spontaneously migrate to the air/water interface, where they self-assemble, forming a monolayer under certain conditions. The spontaneous formation of the NP film at the air/water interface was due to the minimization of the system Helmholtz free energy. However, the extent of surface functionalization was dictated by kinetics. This decouples interfacial ligand exchange from interfacial self-assembly, while maintaining the simplicity of a single system. The interparticle center-to-center distance was dictated by the amine ligand length. The Au NP monolayers exhibit tunable surface plasma resonance and excellent spatial homogeneity, which is useful for surface-enhanced Raman scattering. The "air/water/oil" self-assembly method developed here not only benefits the fundamental understanding of NP ligand conformations, but is also applicable to the manufacture of plasmonic nanoparticle devices with precisely designed optical properties.
Show less - Date Issued
- 2016-10-20
- Identifier
- FSU_libsubv1_wos_000385769800001, 10.1038/srep35339
- Format
- Citation
- Title
- Landau-level Spectroscopy Of Massive Dirac Fermions In Single-crystalline Zrte5 Thin Flakes.
- Creator
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Jiang, Y., Dun, Z. L., Zhou, H. D., Lu, Z., Chen, K.-W., Moon, S., Besara, T., Siegrist, T. M., Baumbach, R. E., Smirnov, D., Jiang, Z.
- Abstract/Description
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We report infrared magnetospectroscopy studies on thin crystals of an emerging Dirac material ZrTe5 near the intrinsic limit. The observed structure of the Landau-level transitions and zero-field infrared absorption indicate a two-dimensional Dirac-like electronic structure, similar to that in graphene but with a small relativistic mass corresponding to a 9.4-meV energy gap. Measurements with circularly polarized light reveal a significant electron-hole asymmetry, which leads to splitting of...
Show moreWe report infrared magnetospectroscopy studies on thin crystals of an emerging Dirac material ZrTe5 near the intrinsic limit. The observed structure of the Landau-level transitions and zero-field infrared absorption indicate a two-dimensional Dirac-like electronic structure, similar to that in graphene but with a small relativistic mass corresponding to a 9.4-meV energy gap. Measurements with circularly polarized light reveal a significant electron-hole asymmetry, which leads to splitting of the Landau-level transitions at high magnetic fields. Our model, based on the Bernevig-Hughes-Zhang effective Hamiltonian, quantitatively explains all observed transitions, determining the values of the Fermi velocity, Dirac mass (or gap), electron-hole asymmetry, and electron and hole g factors.
Show less - Date Issued
- 2017-07-05
- Identifier
- FSU_libsubv1_wos_000405026300001, 10.1103/PhysRevB.96.041101
- Format
- Citation
- Title
- Secondary Building Units, Nets and Bonding in the Chemistry of Metal-Organic Frameworks.
- Creator
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Mendoza-Cortes, Jose L., Tranchemontagne, David J., , Michael, Yaghi, Omar M.
- Abstract/Description
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This critical review presents a comprehensive study of transition-metal carboxylate clusters which may serve as secondary building units (SBUs) towards construction and synthesis of metal-organic frameworks (MOFs). We describe the geometries of 131 SBUs, their connectivity and composition. This contribution presents a comprehensive list of the wide variety of transition-metal carboxylate clusters which may serve as secondary building units (SBUs) in the construction and synthesis of metal...
Show moreThis critical review presents a comprehensive study of transition-metal carboxylate clusters which may serve as secondary building units (SBUs) towards construction and synthesis of metal-organic frameworks (MOFs). We describe the geometries of 131 SBUs, their connectivity and composition. This contribution presents a comprehensive list of the wide variety of transition-metal carboxylate clusters which may serve as secondary building units (SBUs) in the construction and synthesis of metal-organic frameworks. The SBUs discussed here were obtained from a search of molecules and extended structures archived in the Cambridge Structure Database (CSD, version 5.28, January 2007) which included only crystals containing metal carboxylate linkages (241 references).
Show less - Date Issued
- 2009-03-31
- Identifier
- FSU_libsubv1_scholarship_submission_1472222920, 10.1039/b817735j
- Format
- Citation
- Title
- Self-assembly Of Large-scale Crack-free Gold Nanoparticle Films Using A 'drain-to-deposit' Strategy.
- Creator
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Yang, Guang, Hallinan, Daniel T.
- Abstract/Description
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Gold nanoparticles are widely studied due to the ease of controlled synthesis, facile surface modification, and interesting physical properties. However, a technique for depositing large-area, crack-free monolayers on solid substrates is lacking. Herein is presented a method for accomplishing this. Spherical gold nanoparticles were synthesized as an aqueous dispersion. Assembly into monolayers and ligand exchange occurred simultaneously at an organic/aqueous interface. Then the monolayer film...
Show moreGold nanoparticles are widely studied due to the ease of controlled synthesis, facile surface modification, and interesting physical properties. However, a technique for depositing large-area, crack-free monolayers on solid substrates is lacking. Herein is presented a method for accomplishing this. Spherical gold nanoparticles were synthesized as an aqueous dispersion. Assembly into monolayers and ligand exchange occurred simultaneously at an organic/aqueous interface. Then the monolayer film was deposited onto arbitrary solid substrates by slowly pumping out the lower, aqueous phase. This allowed the monolayer film (and liquid-liquid interface) to descend without significant disturbance, eventually reaching substrates contained in the aqueous phase. The resulting macroscopic quality of the films was found to be superior to films transferred by Langmuir techniques. The surface plasmon resonance and Raman enhancement of the films were evaluated and found to be uniform across the surface of each film.
Show less - Date Issued
- 2016-06-03
- Identifier
- FSU_libsubv1_wos_000374767500020, 10.1088/0957-4484/27/22/225604
- Format
- Citation
- Title
- Temperature-pressure phase diagram of cubic Laves phase Au2Pb.
- Creator
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Chen, K. W., Graf, D., Besara, T., Gallagher, A., Kikugawa, N., Balicas, L., Siegrist, T., Shekhter, A., Baumbach, R. E.
- Abstract/Description
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The temperature (T) as a function of pressure (P) phase diagram is reported for the cubic Laves phase compound Au2Pb, which was recently proposed to support linearly dispersing topological bands, together with conventional quadratic bands. At ambient pressure, Au2Pb exhibits several structural phase transitions at T-1 = 97 K, T-2 = 51 K, and T-3 = 40 K with superconductivity below T-c = 1.2 K. Applied pressure results in a rich phase diagram where T-1, T-2, and T-3 evolve strongly with P and...
Show moreThe temperature (T) as a function of pressure (P) phase diagram is reported for the cubic Laves phase compound Au2Pb, which was recently proposed to support linearly dispersing topological bands, together with conventional quadratic bands. At ambient pressure, Au2Pb exhibits several structural phase transitions at T-1 = 97 K, T-2 = 51 K, and T-3 = 40 K with superconductivity below T-c = 1.2 K. Applied pressure results in a rich phase diagram where T-1, T-2, and T-3 evolve strongly with P and a possible new phase is stabilized for P > 0.64 GPa that also supports superconductivity below 1.1 K. These observations suggest that Au2Pb is an ideal system in which to investigate the relationship between structural degrees of freedom, band topology, and resulting anomalous behaviors.
Show less - Date Issued
- 2016-01-19
- Identifier
- FSU_libsubv1_wos_000368486600005, 10.1103/PhysRevB.93.045118
- Format
- Citation
