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Title: An Electrochemical Approach To Measuring Oxidative Stability Of Solid Polymer Electrolytes For Lithium Batteries.
Creator: Hallinan, Daniel T., Rausch, Alexander, McGill, Brandon
Abstract/Description: 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.
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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: Mendoza-Cortes, Jose L., Lucht, Kevin P.
Abstract/Description: 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.
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Date Issued: 2015-09-21
Identifier: FSU_libsubv1_scholarship_submission_1472154701, 10.1021/acs.jpcc.5b07860
Format: Citation

Title: Bulk assembly of organic metal halide nanotubes.
Creator: Lin, Haoran, Zhou, Chenkun, Tian, Yu, Besara, Tiglet, Neu, Jennifer, Siegrist, Theo, Zhou, Yan, Bullock, James, Schanze, Kirk S, Ming, Wenmei, Du, Mao-Hua, Ma, Biwu
Abstract/Description: The organic metal halide hybrids welcome a new member with a one-dimensional (1D) tubular structure. Herein we report the synthesis and characterization of a single crystalline bulk assembly of organic metal halide nanotubes, (CHN)PbBr. In a metal halide nanotube, six face-sharing metal halide dimers (PbBr) connect at the corners to form rings that extend in one dimension, of which the inside and outside surfaces are coated with protonated hexamethylenetetramine (HMTA) cations (CHN). This...
Show moreThe organic metal halide hybrids welcome a new member with a one-dimensional (1D) tubular structure. Herein we report the synthesis and characterization of a single crystalline bulk assembly of organic metal halide nanotubes, (CHN)PbBr. In a metal halide nanotube, six face-sharing metal halide dimers (PbBr) connect at the corners to form rings that extend in one dimension, of which the inside and outside surfaces are coated with protonated hexamethylenetetramine (HMTA) cations (CHN). This unique 1D tubular structure possesses highly localized electronic states with strong quantum confinement, resulting in the formation of self-trapped excitons that give strongly Stokes shifted broadband yellowish-white emission with a photoluminescence quantum efficiency (PLQE) of ∼7%. Having realized single crystalline bulk assemblies of two-dimensional (2D) wells, 1D wires, and now 1D tubes using organic metal halide hybrids, our work significantly advances the research on bulk assemblies of quantum-confined materials.
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Date Issued: 2017-12-01
Identifier: FSU_pmch_29619186, 10.1039/c7sc03675b, PMC5862099, 29619186, 29619186, c7sc03675b
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: 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.
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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: Oparaji, Onyekachi, Zuo, Xiaobing, Hallinan, Daniel T.
Abstract/Description: 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.
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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: Mendoza-Cortes, Jose L, Pramudya, Yohanes
Abstract/Description: 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.
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Date Issued: 2016-10-28
Identifier: FSU_libsubv1_scholarship_submission_1480625626-p, 10.1021/jacs.6b08803
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 (Supplemental Information).
Creator: Mendoza-Cortez, Jose L, Pramudya, Yohanes
Abstract/Description: 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.
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Date Issued: 2016-10-28
Identifier: FSU_libsubv1_scholarship_submission_1480625626-1, 10.1021/jacs.6b08803
Format: Citation

Title: Dirac Cone in two dimensional bilayer graphene by intercalation with V, Nb, and Ta transition metals.
Creator: Pakhira, Srimanta, Lucht, Kevin P., Mendoza-Cortes, Jose L.
Abstract/Description: 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.
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Date Issued: 2017-09-16
Identifier: FSU_libsubv1_scholarship_submission_1519056039_9000b4fa
Format: Citation

Title: Direct detection of neural activity in vitro using magnetic resonance electrical impedance tomography (MREIT).
Creator: Sadleir, Rosalind J, Fu, Fanrui, Falgas, Corey, Holland, Stephen, Boggess, May, Grant, Samuel C, Woo, Eung Je
Abstract/Description: We describe a sequence of experiments performed in vitro to verify the existence of a new magnetic resonance imaging contrast - Magnetic Resonance Electrical Impedance Tomography (MREIT) -sensitive to changes in active membrane conductivity. We compared standard deviations in MREIT phase data from spontaneously active Aplysia abdominal ganglia in an artificial seawater background solution (ASW) with those found after treatment with an excitotoxic solution (KCl). We found significant increases...
Show moreWe describe a sequence of experiments performed in vitro to verify the existence of a new magnetic resonance imaging contrast - Magnetic Resonance Electrical Impedance Tomography (MREIT) -sensitive to changes in active membrane conductivity. We compared standard deviations in MREIT phase data from spontaneously active Aplysia abdominal ganglia in an artificial seawater background solution (ASW) with those found after treatment with an excitotoxic solution (KCl). We found significant increases in MREIT treatment cases, compared to control ganglia subject to extra ASW. This distinction was not found in phase images from the same ganglia using no imaging current. Further, significance and effect size depended on the amplitude of MREIT imaging current used. We conclude that our observations were linked to changes in cell conductivity caused by activity. Functional MREIT may have promise as a more direct method of functional neuroimaging than existing methods that image correlates of blood flow such as BOLD fMRI.
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Date Issued: 2017-11-01
Identifier: FSU_pmch_28818695, 10.1016/j.neuroimage.2017.08.004, PMC5696120, 28818695, 28818695, S1053-8119(17)30651-1
Format: Citation

Title: Distinguishing neuronal from astrocytic subcellular microstructures using in vivo Double Diffusion Encoded 1H MRS at 21.1 T.
Creator: Shemesh, Noam, Rosenberg, Jens T, Dumez, Jean-Nicolas, Grant, Samuel C, Frydman, Lucio
Abstract/Description: Measuring cellular microstructures non-invasively and achieving specificity towards a cell-type population within an interrogated in vivo tissue, remains an outstanding challenge in brain research. Magnetic Resonance Spectroscopy (MRS) provides an opportunity to achieve cellular specificity via the spectral resolution of metabolites such as N-Acetylaspartate (NAA) and myo-Inositol (mI), which are considered neuronal and astrocytic markers, respectively. Yet the information typically obtained...
Show moreMeasuring cellular microstructures non-invasively and achieving specificity towards a cell-type population within an interrogated in vivo tissue, remains an outstanding challenge in brain research. Magnetic Resonance Spectroscopy (MRS) provides an opportunity to achieve cellular specificity via the spectral resolution of metabolites such as N-Acetylaspartate (NAA) and myo-Inositol (mI), which are considered neuronal and astrocytic markers, respectively. Yet the information typically obtained with MRS describes metabolic concentrations, diffusion coefficients or relaxation rates rather than microstructures. Understanding how these metabolites are compartmentalized is a challenging but important goal, which so far has been mainly addressed using diffusion models. Here, we present direct in vivo evidence for the confinement of NAA and mI within sub-cellular components, namely, the randomly oriented process of neurons and astrocytes, respectively. Our approach applied Relaxation Enhanced MRS at ultrahigh (21.1 T) field, and used its high 1H sensitivity to measure restricted diffusion correlations for NAA and mI using a Double Diffusion Encoding (DDE) filter. While very low macroscopic anisotropy was revealed by spatially localized Diffusion Tensor Spectroscopy, DDE displayed characteristic amplitude modulations reporting on confinements in otherwise randomly oriented anisotropic microstructures for both metabolites. This implies that for the chosen set of parameters, the DDE measurements had a biased sensitivity towards NAA and mI sited in the more confined environments of neurites and astrocytic branches, than in the cell somata. These measurements thus provide intrinsic diffusivities and compartment diameters, and revealed subcellular neuronal and astrocytic morphologies in normal in vivo rat brains. The relevance of these measurements towards human applications-which could in turn help understand CNS plasticity as well as diagnose brain diseases-is discussed.
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Date Issued: 2017-10-02
Identifier: FSU_pmch_28968410, 10.1371/journal.pone.0185232, PMC5624579, 28968410, 28968410, PONE-D-17-12913
Format: Citation

Title: Enhanced Gel Formation In Binary Mixtures Of Nanocolloids With Short-range Attraction.
Creator: Harden, James L., Guo, Hongyu, Bertrand, Martine, Shendruk, Tyler N., Ramakrishnan, Subramanian, Leheny, Robert L.
Abstract/Description: Colloidal suspensions transform between fluid and disordered solid states as parameters such as the colloid volume fraction and the strength and nature of the colloidal interactions are varied. Seemingly subtle changes in the characteristics of the colloids can markedly alter the mechanical rigidity and flow behavior of these soft composite materials. This sensitivity creates both a scientific challenge and an opportunity for designing suspensions for specific applications. In this paper, we...
Show moreColloidal suspensions transform between fluid and disordered solid states as parameters such as the colloid volume fraction and the strength and nature of the colloidal interactions are varied. Seemingly subtle changes in the characteristics of the colloids can markedly alter the mechanical rigidity and flow behavior of these soft composite materials. This sensitivity creates both a scientific challenge and an opportunity for designing suspensions for specific applications. In this paper, we report a novel mechanism of gel formation in mixtures of weakly attractive nanocolloids with modest size ratio. Employing a combination of x-ray photon correlation spectroscopy, rheometry, and molecular dynamics simulations, we find that gels are stable at remarkably weaker attraction in mixtures with size ratio near two than in the corresponding monodisperse suspensions. In contrast with depletion-driven gelation at larger size ratio, gel formation in the mixtures is triggered by microphase demixing of the species into dense regions of immobile smaller colloids surrounded by clusters of mobile larger colloids that is not predicted by mean-field thermodynamic considerations. These results point to a new route for tailoring nanostructured colloidal solids through judicious combination of interparticle interaction and size distribution. Published by AIP Publishing.
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Date Issued: 2018-01-28
Identifier: FSU_libsubv1_wos_000424015400053, 10.1063/1.5007038
Format: Citation

Title: Exploring Low Internal Reorganization Energies For Silicene Nanoclusters.
Creator: Pablo-Pedro, Ricardo, Lopez-Rios, Hector, Mendoza-Cortes, Jose-L., Kong, Jing, Fomine, Serguei, Van Voorhis, Troy, Dresselhaus, Mildred S.
Abstract/Description: High-performance materials rely on small reorganization energies to facilitate both charge separation and charge transport. Here, we perform density-functional-theory calculations to predict small reorganization energies of rectangular silicene nanoclusters with hydrogen-passivated edges denoted by H-SiNC. We observe that across all geometries, H-SiNCs feature large electron affinities and highly stabilized anionic states, indicating their potential as n-type materials. Our findings suggest...
Show moreHigh-performance materials rely on small reorganization energies to facilitate both charge separation and charge transport. Here, we perform density-functional-theory calculations to predict small reorganization energies of rectangular silicene nanoclusters with hydrogen-passivated edges denoted by H-SiNC. We observe that across all geometries, H-SiNCs feature large electron affinities and highly stabilized anionic states, indicating their potential as n-type materials. Our findings suggest that fine-tuning the size of H-SiNCs along the "zigzag" and "armchair" directions may permit the design of novel n-type electronic materials and spintronics devices that incorporate both high electron affinities and very low internal reorganization energies.
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Date Issued: 2018-05-09
Identifier: FSU_libsubv1_wos_000433001000001, 10.1103/PhysRevApplied.9.054012
Format: Citation

Title: Flow Of Viscoelastic Fluids Around A Sharp Microfluidic Bend: Role Of Wormlike Micellar Structure.
Creator: Hwang, Margaret Y., Mohammadigoushki, Hadi, Muller, Susan J.
Abstract/Description: 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.
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Date Issued: 2017-04-27
Identifier: FSU_libsubv1_wos_000400249900002, 10.1103/PhysRevFluids.2.043303
Format: Citation

Title: Flow Of Wormlike Micellar Fluids Around A Sharp Bend: Effects Of Branching And Shear-banding.
Creator: Zhang, Yiran, Mohammadigoushki, Hadi, Hwang, Margaret Y., Muller, Susan J.
Abstract/Description: The flow of wormlike micellar solutions around a 90 degrees sharp microfluidic bend was studied using rheometry, flow visualization, and velocimetry. By carefully choosing the composition of the test solutions, all four combinations of linear or branched micelles and shear-banding or non-shear-banding solutions were accessed using four wormlike micellar solutions. The flow behavior of the solutions was examined in similar conditions of about 1
Show moreThe flow of wormlike micellar solutions around a 90 degrees sharp microfluidic bend was studied using rheometry, flow visualization, and velocimetry. By carefully choosing the composition of the test solutions, all four combinations of linear or branched micelles and shear-banding or non-shear-banding solutions were accessed using four wormlike micellar solutions. The flow behavior of the solutions was examined in similar conditions of about 1 < Wi < 300 and 10(-6) < Re < 10(-2). When comparing the flow around the microbend of the two shearbanding solutions with the two non-shear-banding ones, the secondary flows showed distinct differences at about 10< Wi <100. Flow visualization showed that a steady lip vortex formed at the inner upstream corner of the microbend in the non-shear-banding solutions, while a lip (inner upstream corner) vortex and an outer corner vortex formed in the shear-banding solutions. On the other hand, when comparing the solutions with similar rheological characteristics but different micelle morphology (linear versus branched), no significant differences in the flow behavior were observed. These results suggest that shear-banding plays a central role in determining the secondary flow behavior around the microbend, while the effect of micelle morphology is minimal for wormlike micelle solutions. Additional particle tracking velocimetry measurements were carried out both upstream of and around the microbend. The resulting velocity profiles in the shear-banding solutions show marked disagreement with calculations based on the shear-rate-dependent apparent viscosity using the Carreau model. These results suggest that the shear-banding effect on the flow around the microbend could be correlated to the development of a "jetting" flow regime upstream of the bend, which could be a result of the nonmonotonic stress - shear rate relationship in shear-banding wormlike micellar solutions.
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Date Issued: 2018-09-04
Identifier: FSU_libsubv1_wos_000443685600001, 10.1103/PhysRevFluids.3.093301
Format: Citation

Title: Framework Vs. Side-chain Amphidynamic Behaviour In Oligo-(ethylene Oxide) Functionalised Covalent-organic Frameworks.
Creator: Vazquez-Molina, Demetrius A., Pope, Giovanna M., Ezazi, Andrew A., Mendoza-Cortes, Jose L., Harper, James K., Uribe-Romo, Fernando J.
Abstract/Description: We present a family of covalent organic frameworks that have been functionalized with oligo-(ethylene oxide) chains of varying lengths. Because of the open structure of the COFs, the side chains do not interfere with their crystallization obtaining materials with predictable crystal structure. The difference in length of the side-chains allowed for the determination of amphidynamic behaviour with the use of C-13 solid-state NMR relaxation methods. Computational calculations further contribute...
Show moreWe present a family of covalent organic frameworks that have been functionalized with oligo-(ethylene oxide) chains of varying lengths. Because of the open structure of the COFs, the side chains do not interfere with their crystallization obtaining materials with predictable crystal structure. The difference in length of the side-chains allowed for the determination of amphidynamic behaviour with the use of C-13 solid-state NMR relaxation methods. Computational calculations further contribute to understanding the atomistic dynamic behaviour of the different atoms. This study demonstrates the ability to design complex behaviour in organic crystals.
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Date Issued: 2018-06-25
Identifier: FSU_libsubv1_wos_000436029000067, 10.1039/c8cc04292f
Format: Citation

Title: Gold Nanoparticle Monolayers From Sequential Interfacial Ligand Exchange And Migration In A Three-phase System.
Creator: Yang, Guang, Hallinan, Daniel T.
Abstract/Description: 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.
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Date Issued: 2016-10-20
Identifier: FSU_libsubv1_wos_000385769800001, 10.1038/srep35339
Format: Citation

Title: Gold Nanoparticle Monolayers from Sequential Interfacial Ligand Exchange and Migration in a Three-Phase System.
Creator: Yang, Guang, Hallinan, Daniel T
Abstract/Description: 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.
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Date Issued: 2016-10-20
Identifier: FSU_pmch_27762394, 10.1038/srep35339, PMC5071885, 27762394, 27762394, srep35339
Format: Citation

Title: The Influence Of Carrier Gas On Plasma Properties And Hydrogen Peroxide Production In A Nanosecond Pulsed Plasma Discharge Generated In A Water-film Plasma Reactor.
Creator: Wang, Huihui, Wandell, Robert J., Locke, Bruce R.
Abstract/Description: The influence of carrier gas (argon and helium) on the properties of a nanosecond pulsed filamentary discharge propagating along the water surface in a water film plasma reactor, and the effects of plasma properties on the formation of hydrogen peroxide (H2O2) are investigated. The plasma properties, including electron density, gas temperature, and plasma volume, and the hydrogen peroxide production rate and energy yield were measured and compared in both argon and helium discharges. The...
Show moreThe influence of carrier gas (argon and helium) on the properties of a nanosecond pulsed filamentary discharge propagating along the water surface in a water film plasma reactor, and the effects of plasma properties on the formation of hydrogen peroxide (H2O2) are investigated. The plasma properties, including electron density, gas temperature, and plasma volume, and the hydrogen peroxide production rate and energy yield were measured and compared in both argon and helium discharges. The results show that helium plasma is more diffusive compared with the argon plasma, and it has lower electron density and gas temperature but larger volume. The production rates and energy yields of hydrogen peroxide are only slightly higher in the helium plasma although the electron density is much lower. A simple mathematical model with time-dependent fast radical and electron quenching in a small film surrounding the plasma core and with lumped reaction kinetics for H2O2 formation and degradation suggests that the hydroxyl radical (center dot OH) concentration is approximately two times higher in the argon discharge, but the larger volume of the helium leads to about two times more total center dot OH in the helium with correspondingly higher energy yields. The experimental data and model imply that the H2O2 energy yield may increase at lower power (or specific energy density) for both carrier gases.
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Date Issued: 2018-03-07
Identifier: FSU_libsubv1_wos_000424898200002, 10.1088/1361-6463/aaa835
Format: Citation

Title: Influence of grain boundary characteristics on thermal stability in nanotwinned copper.
Creator: Niu, Rongmei, Han, Ke, Su, Yi-Feng, Besara, Tiglet, Siegrist, Theo M, Zuo, Xiaowei
Abstract/Description: High density grain boundaries provide high strength, but may introduce undesirable features, such as high Fermi levels and instability. We investigated the kinetics of recovery and recrystallization of Cu that was manufactured to include both nanotwins (NT) and high-angle columnar boundaries. We used the isothermal Johnson-Mehl-Avrami-Kolmogorov (JMAK) model to estimate activation energy values for recovery and recrystallization and compared those to values derived using the non-isothermal...
Show moreHigh density grain boundaries provide high strength, but may introduce undesirable features, such as high Fermi levels and instability. We investigated the kinetics of recovery and recrystallization of Cu that was manufactured to include both nanotwins (NT) and high-angle columnar boundaries. We used the isothermal Johnson-Mehl-Avrami-Kolmogorov (JMAK) model to estimate activation energy values for recovery and recrystallization and compared those to values derived using the non-isothermal Kissinger equation. The JMAK model hinges on an exponent that expresses the growth mechanism of a material. The exponent for this Cu was close to 0.5, indicating low-dimensional microstructure evolution, which is associated with anisotropic twin coarsening, heterogeneous recrystallization, and high stability. Since this Cu was of high purity, there was a negligible impurity-drag-effect on boundaries. The twin coarsening and heterogeneous recrystallization resulted from migration of high-angle columnar boundaries with their triple junctions in one direction, assisted by the presence of high concentration vacancies at boundaries. Analyses performed by electron energy loss spectroscopy of atomic columns at twin boundaries (TBs) and in the interior showed similar plasma peak shapes and L3 edge positions. This implies that values for conductivity and Fermi level are equal for atoms at TBs and in the interior.
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Date Issued: 2016-08-12
Identifier: FSU_pmch_27514474, 10.1038/srep31410, PMC4981844, 27514474, 27514474, srep31410
Format: Citation

Title: Landau-level Spectroscopy Of Massive Dirac Fermions In Single-crystalline Zrte5 Thin Flakes.
Creator: 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: 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.
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Date Issued: 2017-07-05
Identifier: FSU_libsubv1_wos_000405026300001, 10.1103/PhysRevB.96.041101
Format: Citation

Title: Luminescent Zero-dimensional Organic Metal Halide Hybrids With Near-unity Quantum Efficiency.
Creator: Zhou, Chenkun, Lin, Haoran, Tian, Yu, Yuan, Zhao, Clark, Ronald, Chen, Banghao, van de Burgt, Lambertus J., Wang, Jamie C., Zhou, Yan, Hanson, Kenneth, Meisner, Quinton J., Neu,...
Show moreZhou, Chenkun, Lin, Haoran, Tian, Yu, Yuan, Zhao, Clark, Ronald, Chen, Banghao, van de Burgt, Lambertus J., Wang, Jamie C., Zhou, Yan, Hanson, Kenneth, Meisner, Quinton J., Neu, Jennifer, Besara, Tiglet, Siegrist, Theo, Lambers, Eric, Djurovich, Peter, Ma, Biwu
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Abstract/Description: Single crystalline zero-dimensional (0D) organic-inorganic hybrid materials with perfect host-guest structures have been developed as a new generation of highly efficient light emitters. Here we report a series of lead-free organic metal halide hybrids with a 0D structure, (C4N2H14X)(4)SnX6 (X = Br, I) and (C9NH20)(2)SbX5 (X = Cl), in which the individual metal halide octahedra (SnX64-) and quadrangular pyramids (SbX52-) are completely isolated from each other and surrounded by the organic...
Show moreSingle crystalline zero-dimensional (0D) organic-inorganic hybrid materials with perfect host-guest structures have been developed as a new generation of highly efficient light emitters. Here we report a series of lead-free organic metal halide hybrids with a 0D structure, (C4N2H14X)(4)SnX6 (X = Br, I) and (C9NH20)(2)SbX5 (X = Cl), in which the individual metal halide octahedra (SnX64-) and quadrangular pyramids (SbX52-) are completely isolated from each other and surrounded by the organic ligands C4N2H14X+ and C9NH20+, respectively. The isolation of the photoactive metal halide species by the wide band gap organic ligands leads to no interaction or electronic band formation between the metal halide species, allowing the bulk materials to exhibit the intrinsic properties of the individual metal halide species. These 0D organic metal halide hybrids can also be considered as perfect host-guest systems, with the metal halide species periodically doped in the wide band gap matrix. Highly luminescent, strongly Stokes shifted broadband emissions with photoluminescence quantum efficiencies (PLQEs) of close to unity were realized, as a result of excited state structural reorganization of the individual metal halide species. Our discovery of highly luminescent single crystalline 0D organic-inorganic hybrid materials as perfect host-guest systems opens up a new paradigm in functional materials design.
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Date Issued: 2018-01-21
Identifier: FSU_libsubv1_wos_000422947000005, 10.1039/c7sc04539e
Format: Citation

Title: Luminescent zero-dimensional organic metal halide hybrids with near-unity quantum efficiency.
Creator: Zhou, Chenkun, Lin, Haoran, Tian, Yu, Yuan, Zhao, Clark, Ronald, Chen, Banghao, van de Burgt, Lambertus J, Wang, Jamie C, Zhou, Yan, Hanson, Kenneth, Meisner, Quinton J, Neu,...
Show moreZhou, Chenkun, Lin, Haoran, Tian, Yu, Yuan, Zhao, Clark, Ronald, Chen, Banghao, van de Burgt, Lambertus J, Wang, Jamie C, Zhou, Yan, Hanson, Kenneth, Meisner, Quinton J, Neu, Jennifer, Besara, Tiglet, Siegrist, Theo, Lambers, Eric, Djurovich, Peter, Ma, Biwu
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Abstract/Description: Single crystalline zero-dimensional (0D) organic-inorganic hybrid materials with perfect host-guest structures have been developed as a new generation of highly efficient light emitters. Here we report a series of lead-free organic metal halide hybrids with a 0D structure, (CNHX)SnX (X = Br, I) and (CNH)SbX (X = Cl), in which the individual metal halide octahedra (SnX) and quadrangular pyramids (SbX) are completely isolated from each other and surrounded by the organic ligands CNHX and CNH,...
Show moreSingle crystalline zero-dimensional (0D) organic-inorganic hybrid materials with perfect host-guest structures have been developed as a new generation of highly efficient light emitters. Here we report a series of lead-free organic metal halide hybrids with a 0D structure, (CNHX)SnX (X = Br, I) and (CNH)SbX (X = Cl), in which the individual metal halide octahedra (SnX) and quadrangular pyramids (SbX) are completely isolated from each other and surrounded by the organic ligands CNHX and CNH, respectively. The isolation of the photoactive metal halide species by the wide band gap organic ligands leads to no interaction or electronic band formation between the metal halide species, allowing the bulk materials to exhibit the intrinsic properties of the individual metal halide species. These 0D organic metal halide hybrids can also be considered as perfect host-guest systems, with the metal halide species periodically doped in the wide band gap matrix. Highly luminescent, strongly Stokes shifted broadband emissions with photoluminescence quantum efficiencies (PLQEs) of close to unity were realized, as a result of excited state structural reorganization of the individual metal halide species. Our discovery of highly luminescent single crystalline 0D organic-inorganic hybrid materials as perfect host-guest systems opens up a new paradigm in functional materials design.
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Date Issued: 2017-11-21
Identifier: FSU_pmch_29629122, 10.1039/c7sc04539e, PMC5870054, 29629122, 29629122, c7sc04539e
Format: Citation

Title: One-dimensional organic lead halide perovskites with efficient bluish white-light emission.
Creator: Yuan, Zhao, Zhou, Chenkun, Tian, Yu, Shu, Yu, Messier, Joshua, Wang, Jamie C, van de Burgt, Lambertus J, Kountouriotis, Konstantinos, Xin, Yan, Holt, Ethan, Schanze, Kirk, Clark...
Show moreYuan, Zhao, Zhou, Chenkun, Tian, Yu, Shu, Yu, Messier, Joshua, Wang, Jamie C, van de Burgt, Lambertus J, Kountouriotis, Konstantinos, Xin, Yan, Holt, Ethan, Schanze, Kirk, Clark, Ronald, Siegrist, Theo, Ma, Biwu
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Abstract/Description: Organic-inorganic hybrid metal halide perovskites, an emerging class of solution processable photoactive materials, welcome a new member with a one-dimensional structure. Herein we report the synthesis, crystal structure and photophysical properties of one-dimensional organic lead bromide perovskites, CNHPbBr, in which the edge sharing octahedral lead bromide chains [PbBr ] are surrounded by the organic cations CNH to form the bulk assembly of core-shell quantum wires. This unique one...
Show moreOrganic-inorganic hybrid metal halide perovskites, an emerging class of solution processable photoactive materials, welcome a new member with a one-dimensional structure. Herein we report the synthesis, crystal structure and photophysical properties of one-dimensional organic lead bromide perovskites, CNHPbBr, in which the edge sharing octahedral lead bromide chains [PbBr ] are surrounded by the organic cations CNH to form the bulk assembly of core-shell quantum wires. This unique one-dimensional structure enables strong quantum confinement with the formation of self-trapped excited states that give efficient bluish white-light emissions with photoluminescence quantum efficiencies of approximately 20% for the bulk single crystals and 12% for the microscale crystals. This work verifies once again that one-dimensional systems are favourable for exciton self-trapping to produce highly efficient below-gap broadband luminescence, and opens up a new route towards superior light emitters based on bulk quantum materials.
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Date Issued: 2017-01-04
Identifier: FSU_pmch_28051092, 10.1038/ncomms14051, PMC5216108, 28051092, 28051092, ncomms14051
Format: Citation

Title: Preparation Of Encapsulated Sn-cu@graphite Composite Anode Materials For Lithium-ion Batteries.
Creator: Watson, Venroy, Yeboah, Yaw, Weatherspoon, Mark, Zheng, Jim, Kalu, Egwu Eric
Abstract/Description: Electroless encapsulation of graphite particles with copper-tin alloy (Sn-Cu@graphite) is demonstrated as a feasible anode preparation method that is cost effective and provides both high cyclability and reversible capacity. Heat treatment of the electroless composites at 200 degrees C yielded Sn-Cu@graphite anode composites with a 20 wt.% Sn loading, specific surface area of 22.5 m(2)/g and a 1st discharge capacity of 1074 mAh/g at 0.2C rate. In contrast, the graphite substrate particles...
Show moreElectroless encapsulation of graphite particles with copper-tin alloy (Sn-Cu@graphite) is demonstrated as a feasible anode preparation method that is cost effective and provides both high cyclability and reversible capacity. Heat treatment of the electroless composites at 200 degrees C yielded Sn-Cu@graphite anode composites with a 20 wt.% Sn loading, specific surface area of 22.5 m(2)/g and a 1st discharge capacity of 1074 mAh/g at 0.2C rate. In contrast, the graphite substrate particles used for the encapsulation has a surface area of 2.34 m(2)/g) and a 1st cycle discharge capacity of 327 mAh/g at 0.2 C rate. At the 300th cycle, these capacities decreased to similar to 400 mAh/g and 208 mAh/g for the SnCu@graphite and graphite substrate, respectively. Above 300 cycles, the electroless encapsulated SnCu@graphite anode maintained a capacity higher than that determined experimentally and theoretically for graphite. The electrochemical impedance and cyclic voltammetric results demonstrate that the electroless encapsulated Sn-Cu@graphite anode has very low resistance and high reversible redox reactions. The higher capacity and long term cycling (> 300 cycles) achieved with the electroless composite anodes are attributed to the buffering effect of the electroless Cu in the Sn-Cu alloy encapsulating graphite particles, Sn-Cu@graphite's higher surface area (22.5 m(2)/g), and curvature of the graphite particles. The electroless encapsulated Sn-Cu graphite composite anode materials with extended cycling have potential application for the anode of Li-ion battery.
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Date Issued: 2018-08-01
Identifier: FSU_libsubv1_wos_000441821400059, 10.20964/2018.08.39
Format: Citation

Title: Reaction Mechanism of the Selective Reduction of CO2 to CO by a Tetraaza [CoIIN4H]2+ Complex in the Presence of Protons.
Creator: Garza, Alejandro J., Pakhira, Srimanta, Bell, Alexis T., Mendoza-Cortes, Jose L.
Abstract/Description: The tetraaza [CoIIN4H]2+ complex (\textbf{1}) is remarkable for its ability to selectively reduce CO2 to CO with 45\% Faradaic efficiency and a CO to H2 ratio of 3:2. We employ density functional theory (DFT) to determine the reasons behind the unusual catalytic properties of \textbf{1} and the most likely mechanism for CO2 reduction. The selectivity for CO2 over proton reduction is explained by analyzing the catalyst's affinity for the possible ligands present under typical reaction...
Show moreThe tetraaza [CoIIN4H]2+ complex (\textbf{1}) is remarkable for its ability to selectively reduce CO2 to CO with 45\% Faradaic efficiency and a CO to H2 ratio of 3:2. We employ density functional theory (DFT) to determine the reasons behind the unusual catalytic properties of \textbf{1} and the most likely mechanism for CO2 reduction. The selectivity for CO2 over proton reduction is explained by analyzing the catalyst's affinity for the possible ligands present under typical reaction conditions: acetonitrile, water, CO2, and bicarbonate. After reduction of the catalyst by two electrons, formation of [CoIN4H]+-CO−2 is strongly favored. Based on thermodynamic and kinetic data, we establish that the only likely route for producing CO from here consists of a protonation step to yield [CoIN4H]+-CO2H, followed by reaction with CO2 to form [CoIIN4H]2+-CO and bicarbonate. This conclusion corroborates the idea of a direct role of CO2 as a Lewis acid to assist in {C-O} bond dissociation, a conjecture put forward by other authors to explain recent experimental observations. The pathway to formic acid is predicted to be forbidden by high activation barriers, in accordance with the products that are known to be generated by \textbf{1}. Calculated physical observables such as standard reduction potentials and the turnover frequency for our proposed catalytic cycle are in agreement with available experimental data reported in the literature. The mechanism also makes a prediction that may be experimentally verified: that the rate of CO formation should increase linearly with the partial pressure of CO2.
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Date Issued: 2018
Identifier: FSU_libsubv1_scholarship_submission_1536343798_97dee023, 10.1039/C8CP01963K
Format: Citation

Title: S-Doped MoP Nanoporous Layer Towards High-Efficiency Hydrogen Evolution in pH-Universal Electrolyte.
Creator: Pakhira, Srimanta, Nijamudheen, A., Aguirre-Velez, Carlos I., Mendoza-Cortes, Jose L.
Abstract/Description: In this study, we report a nonprecious metal catalyst for high-efficiency hydrogen evolution reaction (HER). A self-organized S-doped MoP nanoporous layer (S-MoP NPL) is achieved through a facile electrochemical anodic process and a two-step chemical vapor deposition treatment, which was directly used as a binder-free catalyst for HER in pH-universal electrolytes. SMoP NPL exhibits HER behavior with a low overpotential of 86 mV at 10 mA cm−1 and low Tafel slope of 34 mV dec−1 in acidic...
Show moreIn this study, we report a nonprecious metal catalyst for high-efficiency hydrogen evolution reaction (HER). A self-organized S-doped MoP nanoporous layer (S-MoP NPL) is achieved through a facile electrochemical anodic process and a two-step chemical vapor deposition treatment, which was directly used as a binder-free catalyst for HER in pH-universal electrolytes. SMoP NPL exhibits HER behavior with a low overpotential of 86 mV at 10 mA cm−1 and low Tafel slope of 34 mV dec−1 in acidic solution. Moreover, S-MoP NPL also shows high HER activity in basic and neutral electrolytes. Density functional theory (DFT) computations were carried out to support our experiment. The calculations show that the H2 formation (via Volmer−Heyrovsky mechanism) from the reaction of a metal (Mo) absorbed hydride with a solvated proton is favored over S-MoP than MoS2. Both experimental and computational studies demonstrate that the extraordinary HER activity and stability performance displayed by a MoP catalyst can be enhanced by S-doping, opening up a promising paradigm for the conscious design of high-performance nonprecious metal catalyst for hydrogen generation.
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Date Issued: 2018-12-18
Identifier: FSU_libsubv1_scholarship_submission_1551725486_98e8698a, 10.1021/acscatal.8b04291
Format: Citation

Title: Scaling Laws For Polymer Chains Grafted Onto Nanoparticles.
Creator: Yang, Guang, Kim, Kyoungmin, Wang, Wentao, Chen, Banghao, Mattoussi, Hedi, Hallinan, Daniel T.
Abstract/Description: An experimental approach is presented for identifying the scaling laws for polymer chains grafted onto gold nanoparticles. Poly(ethylene oxide) of various molecular weights are grafted onto gold nanoparticles via thiol end-functional groups. The polymer-grafted nanoparticles are self-assembled into monolayers from solvents of different quality. Over a significant range of graft densities, nanoparticle monolayers deposited from good (athermal) solvent exhibit particle spacing that scales...
Show moreAn experimental approach is presented for identifying the scaling laws for polymer chains grafted onto gold nanoparticles. Poly(ethylene oxide) of various molecular weights are grafted onto gold nanoparticles via thiol end-functional groups. The polymer-grafted nanoparticles are self-assembled into monolayers from solvents of different quality. Over a significant range of graft densities, nanoparticle monolayers deposited from good (athermal) solvent exhibit particle spacing that scales according to theoretical predictions for chains in dilute solution. This unexpected result for ordered nanoparticle monolayers is discussed in the context of the deposition process. In monolayers deposited from theta solvent, molecular weight scaling of particle spacing breaks down, possibly due to chain length dependence of solvent quality. In poor solvent, the structure of nanoparticle assemblies is not sufficiently ordered to obtain reliable measurements, possibly due to loss of nanoparticle dispersion. This approach opens up the possibility for accurate measurement of the effect of solvent on grafted chain scaling in nanoparticle assemblies.
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Date Issued: 2018-04-01
Identifier: FSU_libsubv1_wos_000430396100001, 10.1002/macp.201700417
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: 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).
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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: Yang, Guang, Hallinan, Daniel T.
Abstract/Description: 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.
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Date Issued: 2016-06-03
Identifier: FSU_libsubv1_wos_000374767500020, 10.1088/0957-4484/27/22/225604
Format: Citation

Title: Structural Dynamics Of Strongly Segregated Block Copolymer Electrolytes.
Creator: Oparaji, Onyekachi, Narayanan, Suresh, Sandy, Alec, Ramakrishnan, Subramanian, Hallinan, Daniel
Abstract/Description: Polymer electrolytes are promising materials for high energy density rechargeable batteries. However, they have low ion transport rates and gradually lose electrode adhesion during cycling. These effects are dependent on polymer structure and dynamics. This motivates an investigation of diblock copolymer electrolyte dynamics. Structural and stress relaxations have been measured with X-ray photon correlation spectroscopy (XPCS) and rheology, respectively, as a function of salt concentration...
Show morePolymer electrolytes are promising materials for high energy density rechargeable batteries. However, they have low ion transport rates and gradually lose electrode adhesion during cycling. These effects are dependent on polymer structure and dynamics. This motivates an investigation of diblock copolymer electrolyte dynamics. Structural and stress relaxations have been measured with X-ray photon correlation spectroscopy (XPCS) and rheology, respectively, as a function of salt concentration and temperature. The polymer electrolyte studied in this work is a mixture of poly(styrene-b-ethylene oxide), SEO, and lithium bistrifluoromethanesulfonimide (LiTFSI). Results from XPCS experiments showed hyperdiffusive motion for various lithium salt concentrations and at varying temperatures, which is indicative of soft glassy materials. This behavior is attributed to cooperative dynamics. The decay time was a weak, nonmonotonic function of salt concentration and decreased with increasing temperature, in an Arrhenius fashion. In contrast, the shear modulus decreased with increasing salt concentration and increasing temperature. The entanglement relaxation from rheological measurements followed Vogel-Fulcher-Tammann behavior. The structural decay time was slower than the entanglement relaxation time at temperatures above the glass transition temperature, but they were approximately equal at Tg regardless of salt concentration. This may indicate a fundamental connection between cooperative structural motion and polymer chain motion in this material.
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Date Issued: 2018-04-10
Identifier: FSU_libsubv1_wos_000430022000020, 10.1021/acs.macromol.7b01803
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: 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.
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Date Issued: 2016-01-19
Identifier: FSU_libsubv1_wos_000368486600005, 10.1103/PhysRevB.93.045118
Format: Citation

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