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(1 - 6 of 6)
- Title
- Birnessite: A Layered Manganese Oxide to Capture Sunlight for Water-Splitting Catalysis.
- Creator
- 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
- 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
- Design Principles for High H2 Storage Using Chelation of Abundant Transition Metals in Covalent Organic Frameworks for 0-700 bar at 298 K.
- Creator
- 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
- Gold Nanoparticle Monolayers From Sequential Interfacial Ligand Exchange And Migration In A Three-phase System.
- Creator
- 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
- Secondary Building Units, Nets and Bonding in the Chemistry of Metal-Organic Frameworks.
- Creator
- 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
- Temperature-pressure phase diagram of cubic Laves phase Au2Pb.
- Creator
- 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
