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Chemistry Publications

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Full-Text Articles in Physical Sciences and Mathematics

Non-Equilibrium Growth Of Metal Clusters On A Layered Material: Cu On Mos2, Dapeng Jing, Ann Lii-Rosales, King C. Lai, Qiang Li, Jaeyoun Kim, Michael C. Tringides, James W. Evans, Patricia A. Thiel May 2020

Non-Equilibrium Growth Of Metal Clusters On A Layered Material: Cu On Mos2, Dapeng Jing, Ann Lii-Rosales, King C. Lai, Qiang Li, Jaeyoun Kim, Michael C. Tringides, James W. Evans, Patricia A. Thiel

Chemistry Publications

We use a variety of experimental techniques to characterize Cu clusters on bulk MoS2 formed via physical vapor deposition of Cu in ultrahigh vacuum, at temperatures ranging from 300 K to 900 K. We find that large facetted clusters grow at elevated temperatures, using high Cu exposures. The cluster size distribution is bimodal, and under some conditions, large clusters are surrounded by a denuded zone. We propose that defect-mediated nucleation, and coarsening during deposition, are both operative in this system. At 780 K, a surprising type of facetted cluster emerges, and at 900 K this type predominates: pyramidal clusters with ...


Magnetic Ionic Liquids As Solvents For Rna Extraction And Preservation, Chenghui Zhu, Marcelino Varona, Jared L. Anderson May 2020

Magnetic Ionic Liquids As Solvents For Rna Extraction And Preservation, Chenghui Zhu, Marcelino Varona, Jared L. Anderson

Chemistry Publications

Ribonucleic acid (RNA) is particularly sensitive to enzymatic degradation by endonucleases prior to sample analysis. In-field preservation has been a challenge for RNA sample preparation. Very recently, hydrophobic magnetic ionic liquids (MIL) have shown significant promise in the area of RNA extraction. In this study, MILs were synthesized and employed as solvents for the extraction and preservation of RNA in aqueous solution. RNA samples obtained from yeast cells were extracted and preserved by the trihexyl(tetradecyl) phosphonium tris(hexafluoroacetylaceto)cobaltate(II) ([P66614+][Co(hfacac)3–]) and trihexyl(tetradecyl) phosphonium tris(phenyltrifluoroacetylaceto)cobaltate(II) ([P66614+][Co(Phtfacac)3–]) MIL with a ...


Spectral Narrowing Accompanies Enhanced Spatial Resolution In Saturated Coherent Anti-Stokes Raman Scattering (Cars): Comparisons Of Experiment And Theory, Avinash Singh, Kalyan Santra, Xueyu Song, Jacob W. Petrich, Emily A. Smith May 2020

Spectral Narrowing Accompanies Enhanced Spatial Resolution In Saturated Coherent Anti-Stokes Raman Scattering (Cars): Comparisons Of Experiment And Theory, Avinash Singh, Kalyan Santra, Xueyu Song, Jacob W. Petrich, Emily A. Smith

Chemistry Publications

We demonstrate theoretically and confirm experimentally the mechanism by which spectral narrowing accompanies enhanced spatial resolution in a saturated coherent anti-Stokes Raman scattering (CARS) signal that is demodulated at the third harmonic (3f) of the pump modulation frequency (f). Under these modulation conditions, theory predicts a narrowing of the full width at half-maximum (FWHM) of the CARS spectrum by a factor of 2.0 with respect to that of the spectrum obtained by demodulation at the fundamental frequency. Theory also predicts an improvement of spatial resolution by a factor of 1.7. Experimentally, narrowing of the FWHM of the ...


Quantum Chemical Lipophilicities Of Antimalarial Drugs In Relation To Terminal Half-Life, Joseph D. Alia, Sheila Karl, Tyler D. Kelly Mar 2020

Quantum Chemical Lipophilicities Of Antimalarial Drugs In Relation To Terminal Half-Life, Joseph D. Alia, Sheila Karl, Tyler D. Kelly

Chemistry Publications

According to the WHO, artemisinin-based combination therapies (ACTs) have been integral to the recent reduction in deaths due to Plasmodium falciparum malaria. ACT-resistant strains are an emerging problem and have evolved altered developmental stages, reducing exposure of the most susceptible stages to artemisinin drugs in popular ACTs. Lipophilicity, log Kow, is a guide in understanding and predicting pharmacokinetic properties such as terminal half-life which alters drug exposure. Consistent log Kow values are not necessarily available for artemisinin derivatives designed to extend terminal half-life, increase bioavailability, and reduce neurotoxicity. For other drugs used in ACTs, an assortment of experimental ...


Direct Photorelease Of Alcohols From Boron-Alkylated Bodipy Photocages, Julie A. Peterson, Logan J. Fischer, Elizabeth J. Gehrmann, Pradeep Shrestha, Ding Yuan, Chamari S. Wijesooriya, Emily A. Smith, Arthur H. Winter Mar 2020

Direct Photorelease Of Alcohols From Boron-Alkylated Bodipy Photocages, Julie A. Peterson, Logan J. Fischer, Elizabeth J. Gehrmann, Pradeep Shrestha, Ding Yuan, Chamari S. Wijesooriya, Emily A. Smith, Arthur H. Winter

Chemistry Publications

BODIPY photocages allow release of substrates us-ing visible light irradiation. They have the drawback of requiring reasonably good leaving groups for photorelease. Photorelease of alcohols is often accomplished by attachment with carbonate linkages, which upon photorelease liberate CO2 and gen-erate the alcohol. Here, we show that boron-alkylated BODIPY photocages are capable of directly photoreleasing both aliphatic alcohols and phenols upon irradiation via photocleavage of ether linkages. Direct photorelease of a hydroxycoumarin dye was demonstrated in living HeLa cells.


Intermetallic Nanocatalysts From Heterobimetallic Group 10–14 Pyridine-2-Thiolate Precursors, Carena L. Daniels, Megan Knobeloch, Philip Yox, Marquix A.S. Adamson, Yunhua Chen, Rick W. Dorn, Hao Wu, Guoquan Zhou, Huajun Fan, Aaron J. Rossini, Javier Vela Mar 2020

Intermetallic Nanocatalysts From Heterobimetallic Group 10–14 Pyridine-2-Thiolate Precursors, Carena L. Daniels, Megan Knobeloch, Philip Yox, Marquix A.S. Adamson, Yunhua Chen, Rick W. Dorn, Hao Wu, Guoquan Zhou, Huajun Fan, Aaron J. Rossini, Javier Vela

Chemistry Publications

Intermetallic compounds are atomically ordered inorganic materials containing two or more transition metals and main-group elements in unique crystal structures. Intermetallics based on group 10 and group 14 metals have shown enhanced activity, selectivity, and durability in comparison to simple metals and alloys in many catalytic reactions. While high-temperature solid-state methods to prepare intermetallic compounds exist, softer synthetic methods can provide key advantages, such as enabling the preparation of metastable phases or of smaller particles with increased surface areas for catalysis. Here, we study a generalized family of heterobimetallic precursors to binary intermetallics, each containing a group 10 metal and ...


The Surface Termination Of Cspbbr3 Perovskite Quantum Dots Determined By Solid-State Nmr Spectroscopy, Yunhua Chen, Sara R. Smock, Anne H. Flintgruber, Frederic A. Perras, Richard L. Brutchey, Aaron J. Rossini Mar 2020

The Surface Termination Of Cspbbr3 Perovskite Quantum Dots Determined By Solid-State Nmr Spectroscopy, Yunhua Chen, Sara R. Smock, Anne H. Flintgruber, Frederic A. Perras, Richard L. Brutchey, Aaron J. Rossini

Chemistry Publications

Cesium lead halide perovskite quantum dots (QDs) have gained significant attention as next-generation optoelectronic materials; however, their properties are highly dependent on their surface chemistry. The surfaces of cuboidal CsPbBr3 QDs have been intensively studied by both theoretical and experimental techniques, but fundamental questions still remain about the atomic termination of the QDs. The binding sites and modes of ligands at the surface remain unproven. Herein, we demonstrate that solid-state NMR spectroscopy allows the unambiguous assignments of organic surface ligands via 1H, 13C, and 31P NMR. Surface-selective 133Cs solid-state NMR spectra show the presence of an additional 133Cs NMR signal ...


Identifying The Molecular Edge Termination Of Exfoliated Hexagonal Boron Nitride Nanosheets With Solid-State Nmr Spectroscopy And Plane-Wave Dft Calculations, Rick W. Dorn, Matthew J. Ryan, Tae-Hoon Kim, Tian Wei Goh, Patrick M. Heintz, Lin Zhou, Wenyu Huang, Aaron J. Rossini Feb 2020

Identifying The Molecular Edge Termination Of Exfoliated Hexagonal Boron Nitride Nanosheets With Solid-State Nmr Spectroscopy And Plane-Wave Dft Calculations, Rick W. Dorn, Matthew J. Ryan, Tae-Hoon Kim, Tian Wei Goh, Patrick M. Heintz, Lin Zhou, Wenyu Huang, Aaron J. Rossini

Chemistry Publications

Hexagonal boron nitride nanosheets (h-BNNS), the isoelectronic analog to graphene, have received interest over the past decade due to their high thermal oxidative resistance, high bandgap, catalytic activity, and low cost. The functional groups that terminate boron and nitrogen zigzag and/or armchair edges directly affect their chemical, physical, and electronic properties. However, an understanding of the molecular edge termination present in h-BNNS is lacking. Here, high-resolution magic-angle spinning (MAS) solid-state NMR (SSNMR) spectroscopy, and plane-wave density-functional theory (DFT) calculations are used to determine the molecular edge termination in exfoliated h-BNNS. 1H → 11B cross-polarization MAS (CPMAS) SSNMR ...


Spin Delocalization, Polarization, And London Dispersion Forces Govern The Formation Of Diradical Pimers, Joshua P. Peterson, Arkady Ellern, Arthur H. Winter Feb 2020

Spin Delocalization, Polarization, And London Dispersion Forces Govern The Formation Of Diradical Pimers, Joshua P. Peterson, Arkady Ellern, Arthur H. Winter

Chemistry Publications

Some free radicals are stable enough to be isolated, but most are either unstable transient species or exist as metastable species in equilibrium with a dimeric form, usually a spin-paired sigma dimer or a pi dimer (pimer). To gain insight into the different modes of dimerization, we synthesized and evaluated a library of 15 aryl dicyanomethyl radicals in order to probe what structural and molecular parameters lead to σ- versus π-dimerization. We evaluated the divergent dimerization behavior by measuring the strength of each radical association by variable-temperature electron paramagnetic resonance spectroscopy, determining the mode of dimerization (σ- or π-dimer) by ...


Fundamentals Of Au(111) Surface Dynamics: Coarsening Of 2d Au Islands, Peter M. Spurgeon, King C. Lai, Yong Han, James W. Evans, Patricia A. Thiel Feb 2020

Fundamentals Of Au(111) Surface Dynamics: Coarsening Of 2d Au Islands, Peter M. Spurgeon, King C. Lai, Yong Han, James W. Evans, Patricia A. Thiel

Chemistry Publications

Au(111) surfaces play a central role in many applications, yet studies of fundamental aspects of their dynamics are limited. Thus, using Scanning Tunneling Microscopy (STM) at 300 K, we analyze the coarsening of first-layer 2D Au islands directly on the Au(111) substrate, and also of second-layer 2D Au islands. Specifically, we monitor the decay of Au first-layer islands with areas of about 100-500 nm^2 in the vicinity of larger islands or extended step edges over a period of approximately 40 hours - the relevant time scale for this process. Experimentally observed behavior is captured by analytic theory for ...


Anomalous Electronic Properties Of Iodous Materials: Application To High-Spin Reactive Intermediates And Conjugated Polymers, Yunfan Qiu, Arthur Winter Feb 2020

Anomalous Electronic Properties Of Iodous Materials: Application To High-Spin Reactive Intermediates And Conjugated Polymers, Yunfan Qiu, Arthur Winter

Chemistry Publications

Manipulating frontier orbital energies of aromatic molecules with substituents is key to a variety of chemical and material applications. Here, we investigate a simple strategy for achieving high-energy in-plane orbitals for aromatics simply by positioning iodine atoms next to each other. The lone pair orbitals on the iodines mix to give a high-energy in-plane σ-antibonding orbital as the highest occupied molecular orbital (HOMO). We show that this effect can be used to manipulate orbital gaps, the symmetry of the highest occupied orbital, and the adopted electronic state for reactive intermediates. This electronic effect is not limited to reactive intermediates, and ...


Silica-Supported Organolanthanum Catalysts For C–O Bond Cleavage In Epoxides, Zhuoran Wang, Smita Patnaik, Naresh Eedugurala, J. Sebastián Manzano, Igor I. Slowing, Takeshi Kobayashi, Aaron D. Sadow, Marek Pruski Feb 2020

Silica-Supported Organolanthanum Catalysts For C–O Bond Cleavage In Epoxides, Zhuoran Wang, Smita Patnaik, Naresh Eedugurala, J. Sebastián Manzano, Igor I. Slowing, Takeshi Kobayashi, Aaron D. Sadow, Marek Pruski

Chemistry Publications

Single-site organolanthanum complexes supported on mesoporous silica nanoparticles, La{C(SiHMe2)3}n@MSNs, catalyze the ring-opening hydroboration reaction of aliphatic and styrenic epoxides with pinacolborane (HBpin). The surface-bound complexes, synthesized by reaction of the homoleptic tris(alkyl)lanthanum La{C(SiHMe2)3}3 and SBA-type MSN treated at 700 °C (MSN700), are mostly monopodal ≡SiO—La{C(SiHMe2)3}2 and contain an average of one bridging La↼H—Si per alkyl ligand. This structure was established through a combination of solid-state NMR (SSNMR) experiments, including J-resolved SiH coupling and quantitative 29Si measurements, diffuse reflectance IR, and elemental ...


Shapes Of Fe Nanocrystals Encapsulated At The Graphite Surface, Ann Lii-Rosales, Yong Han, Scott E. Julien, Olivier Pierre-Louis, Dapeng Jing, Kai-Tak Wan, Michael C. Tringides, James W. Evans, Patricia A. Thiel Feb 2020

Shapes Of Fe Nanocrystals Encapsulated At The Graphite Surface, Ann Lii-Rosales, Yong Han, Scott E. Julien, Olivier Pierre-Louis, Dapeng Jing, Kai-Tak Wan, Michael C. Tringides, James W. Evans, Patricia A. Thiel

Chemistry Publications

We describe and analyze in detail the shapes of Fe islands encapsulated under the top graphene layers in graphite. Shapes are interrogated using scanning tunneling microscopy. The main outputs of the shape analysis are the slope of the graphene membrane around the perimeter of the island, and the aspect ratio of the central metal cluster. Modeling primarily uses a continuum elasticity (CE) model. As input to the CE model, we use density functional theory to calculate the surface energy of Fe, and the adhesion energies between Fe and graphene or graphite. We use the shaft-loaded blister test (SLBT) model to ...


Vacuum-Assisted Sorbent Extraction: An Analytical Methodology For The Determination Of Ultraviolet Filters In Environmental Samples, María Trujillo-Rodríguez, Jared L. Anderson, Sage J. B. Dunham, Victoria L. Noad, Daniel B. Cardin Feb 2020

Vacuum-Assisted Sorbent Extraction: An Analytical Methodology For The Determination Of Ultraviolet Filters In Environmental Samples, María Trujillo-Rodríguez, Jared L. Anderson, Sage J. B. Dunham, Victoria L. Noad, Daniel B. Cardin

Chemistry Publications

Vacuum-assisted sorbent extraction (VASE) has been applied for the first time in the determination of UV filters in water samples in combination with gas chromatography-mass spectrometry. VASE is a variant of headspace extraction which was developed in conjunction with the sorbent pen (SP) technology. This technique combines the advantages of both stir-bar assisted extraction and headspace solid-phase microextraction. The SP traps allowed both reduced pressure in-vial extraction and direct thermal desorption via a unique gas chromatographic injection port. The main parameters that affect the performance of VASE, including both extraction and desorption conditions, were extensively optimized. Under optimum conditions, extraction ...


Adsorption, Intercalation, Diffusion, And Adhesion Of Cu At The 2h−Mos2 (0001) Surface From First-Principles Calculations, Yong Han, Michael C. Tringides, James W. Evans, Patricia A. Thiel Feb 2020

Adsorption, Intercalation, Diffusion, And Adhesion Of Cu At The 2h−Mos2 (0001) Surface From First-Principles Calculations, Yong Han, Michael C. Tringides, James W. Evans, Patricia A. Thiel

Chemistry Publications

Study of the adsorption of a transition metal on the surface of a layered material and the possible subsequent intercalation into that layered material is of fundamental interest and potential technological importance. In the present work, we choose the transition metal Cu as the adsorbate or intercalant and 2H-MoS2 as the layered material. Energetics are calculated characterizing four of the most basic surface and interfacial phenomena: adsorption, intercalation, diffusion, and adhesion. Using first-principles density functional theory (DFT), we find that intercalating a Cu atom into the van der Waals (vdW) gap below the MoS2 (0001) surface is 0.665 eV ...


Silicene, Siloxene, Or Silicane? Revealing The Structure And Optical Properties Of Silicon Nanosheets Derived From Calcium Disilicide, Bradley J. Ryan, Michael P. Hanrahan, Yujie Wang, Utkarsh Ramesh, Charles K. A. Nyamekye, Rainie D. Nelson, Zhiyan Liu, Chuankun Huang, Bevan Whitehead, Jigang Wang, Luke T. Roling, Emily A. Smith, Aaron J. Rossini, Matthew G. Panthani Jan 2020

Silicene, Siloxene, Or Silicane? Revealing The Structure And Optical Properties Of Silicon Nanosheets Derived From Calcium Disilicide, Bradley J. Ryan, Michael P. Hanrahan, Yujie Wang, Utkarsh Ramesh, Charles K. A. Nyamekye, Rainie D. Nelson, Zhiyan Liu, Chuankun Huang, Bevan Whitehead, Jigang Wang, Luke T. Roling, Emily A. Smith, Aaron J. Rossini, Matthew G. Panthani

Chemistry Publications

Si-nanosheets (Si-NSs) have recently attracted considerable attention due to their potential as next-generation materials for electronic, optoelectronic, spintronic, and catalytic applications. Even though monolayer Si-NSs were first synthesized over 150 years ago via topotactic deintercalation of CaSi2, there is a lack of consensus within the literature regarding the structure and optical properties of this material. Herein, we provide conclusive evidence of the structural and chemical properties of Si-NSs produced by the deintercalation of CaSi2 with cold (~ –30 °C) aqueous HCl, and characterize their optical properties. We use a wide range of techniques, including XRD, FTIR, Raman, solid-state NMR, SEM, TEM ...


Mild And Selective Hydrogenation Of Nitrate To Ammonia In The Absence Of Noble Metals, Lin Wei, Da-Jiang Liu, Bryan A. Rosales, James W. Evans, Javier Vela Jan 2020

Mild And Selective Hydrogenation Of Nitrate To Ammonia In The Absence Of Noble Metals, Lin Wei, Da-Jiang Liu, Bryan A. Rosales, James W. Evans, Javier Vela

Chemistry Publications

Motivated by increased awareness about nitrate contamination of surface waters and its deleterious effects in human and animal health, we sought an alternative, non-noble metal catalyst for the chemical degradation of nitrate. First row transition metal phosphides recently emerged as excellent alternatives for hydrogen evolution and hydrotreating reactions. We demonstrate that a key member of this family, Ni2P, readily hydrogenates nitrate (NO3–) to ammonia (NH3) near ambient conditions with very high selectivity (96%). One of the few non-precious metal-based catalysts for this transformation, and among ca. 1% of catalysts with NH3 selectivity, Ni2P can be recycled multiple times with limited ...


Identification Of An Ags2 Complex On Ag(110), Peter M. Spurgeon, Da-Jiang Liu, Junepyo Oh, Yousoo Kim, Patricia A. Thiel Dec 2019

Identification Of An Ags2 Complex On Ag(110), Peter M. Spurgeon, Da-Jiang Liu, Junepyo Oh, Yousoo Kim, Patricia A. Thiel

Chemistry Publications

Adsorbed sulfur has been investigated on the Ag(110) surface at two different coverages, 0.02 and 0.25 monolayers. At the lower coverage, only sulfur adatoms are present. At the higher coverage, there are additional bright features which we identify as linear, independent AgS2 complexes. This identification is based upon density functional theory (DFT) and its comparison with experimental observations including bias dependence and separation between complexes. DFT also predicts the absence of AgS2 complexes at low coverage, and the development of AgS2 complexes around a coverage of 0.25 monolayers of sulfur, as is experimentally observed. To our ...


Macroscale Control Of Reactivity Using 3d Printed Materials With Intrinsic Catalytic Properties, J. Sebastián Manzano, Hsin Wang, Long Qi, Igor I. Slowing Dec 2019

Macroscale Control Of Reactivity Using 3d Printed Materials With Intrinsic Catalytic Properties, J. Sebastián Manzano, Hsin Wang, Long Qi, Igor I. Slowing

Chemistry Publications

The morphology of heterogeneous catalysts can impact their performance by controlling the efficiency of heat and mass transfer. However, standard manufacturing methods such as extrusion or pelleting offer little options for optimizing catalyst shape. Herein, stereolithographic (SLA) 3D printing is used to directly produce catalysts with controlled morphologies to enhance their performance. A series of chemically active magnetic stir-bar compartments (SBC) were 3D printed and used as catalysts for sucrose hydrolysis. The SBCs were composed of acrylic acid (AA) and 1,6-hexanediol diacrylate (HDDA) which provided acid sites and hydrophobic crosslinking domains, respectively. Fixing the surface area and the number ...


Nanosecond, Time-Resolved Shift Of The Photoluminescence Spectra Of Organic, Lead-Halide Perovskites Reveals Structural Features Resulting From Excess Organic Ammonium Halide, Ujjal Bhattacharjee, Long Men, Han Mai, Daniel Freppon, Emily A. Smith, Javier Vela, Jacob W. Petrich Dec 2019

Nanosecond, Time-Resolved Shift Of The Photoluminescence Spectra Of Organic, Lead-Halide Perovskites Reveals Structural Features Resulting From Excess Organic Ammonium Halide, Ujjal Bhattacharjee, Long Men, Han Mai, Daniel Freppon, Emily A. Smith, Javier Vela, Jacob W. Petrich

Chemistry Publications

The effort to drive solution-based perovskite solar cells towards higher efficiency has been considerable, reaching over 24%. Such progress has been made possible by the low-energy barrier to crystallization. The low-energy barrier in the reverse direction, however, also renders them susceptible to dissociation from heat, moisture, and photoexcitation. Consequently, studies that provide information on the stability of perovskites are of considerable importance. It has been reported that perovskite crystals formed using different stoichiometries of the organic precursors and metal halide are equivalent. Our findings, however, suggest that the difference in reaction pathways affects the quality of the final crystal and ...


Bodipy-Caged Photoactivated Inhibitors Of Cathepsin B Flip The Light Switch On Cancer Cell Apoptosis, Nicholas P. Toupin, Karan Arora, Pradeep Shrestha, Julie A. Peterson, Logan J. Fischer, Erandi Rajagurubandara, Izabela Podgorski, Arthur H. Winter, Jeremy J. Kodanko Nov 2019

Bodipy-Caged Photoactivated Inhibitors Of Cathepsin B Flip The Light Switch On Cancer Cell Apoptosis, Nicholas P. Toupin, Karan Arora, Pradeep Shrestha, Julie A. Peterson, Logan J. Fischer, Erandi Rajagurubandara, Izabela Podgorski, Arthur H. Winter, Jeremy J. Kodanko

Chemistry Publications

Acquired resistance to apoptotic agents is a long-standing challenge in cancer treatment. Cathepsin B (CTSB) is an enzyme which, among many essential functions, promotes apoptosis during cellular stress through regulation of intracelllular proteolytic networks on the minute timescale. Recent data indicate that CTSB inhibition may be a promising method to steer cells away from apoptotic death towards necrosis, a mechanism of cell death that can overcome resistance to apoptotic agents, stimulate an immune response and promote anti-tumor immunity. Unfortunately, rapid and selective intracellular inactivation of CTSB has not been possible. However, here we report on the synthesis and characterization of ...


Integrating The Molecular Basis Of Sustainability Into General Chemistry Through Systems Thinking, Peter G. Mahaffy, Stephen A. Matlin, J. Marc Whalen, Thomas A. Holme Nov 2019

Integrating The Molecular Basis Of Sustainability Into General Chemistry Through Systems Thinking, Peter G. Mahaffy, Stephen A. Matlin, J. Marc Whalen, Thomas A. Holme

Chemistry Publications

The flow of materials and energy through society is an integral but poorly visible element of global sustainability agendas such as the Planetary Boundaries Framework and the UN Sustainable Development Goals (UNSDG). Given that the primary activities of chemistry are to analyze, synthesize, and transform matter, the practice of chemistry has a great deal to contribute to sustainability science, which in turn should play an increasingly important role in reshaping the practice of chemistry. Success in integrating sustainability considerations into the practice of chemistry implies a substantial role for chemistry education to better equip students to address the sustainability of ...


Condensed Phase Deactivation Of Solid Brønsted Acids In The Dehydration Of Fructose To Hydroxymethylfurfural, Robert L. Johnson, Frédéric A. Perras, Michael P. Hanrahan, Max A. Mellmer, Thomas Garrison, Takeshi Kobayashi, James A. Dumesic, Marek Pruski, Aaron Rossini, Brent H. Shanks Oct 2019

Condensed Phase Deactivation Of Solid Brønsted Acids In The Dehydration Of Fructose To Hydroxymethylfurfural, Robert L. Johnson, Frédéric A. Perras, Michael P. Hanrahan, Max A. Mellmer, Thomas Garrison, Takeshi Kobayashi, James A. Dumesic, Marek Pruski, Aaron Rossini, Brent H. Shanks

Chemistry Publications

Catalyst deactivation resulting from the hydrothermal leaching of sulfonic acid residues and the deposition of carbonaceous residues was studied using condensed phase flow reactor experiments along with state-of-the-art solid-state NMR. Several commercially available sulfonic acid-containing heterogeneous Bronsted acids were compared by measuring the rates of sulfonic acid breakdown at hydrothermal flow conditions of 160 degrees C. Amberlyst 45 was found to show higher hydrothermal stability when compared to both Nafion and Amberlyst 15, with <10% loss in acidity after 48 h. The dehydration reaction of fructose to hydroxymethylfurfural (HMF) was used as a model system to compare deactivation rates from carbon deposition (fouling) to those from sulfur leaching, and deactivation from fouling was shown to be dramatically faster than that from sulfonic acid leaching alone. Fouling rates were then investigated in greater detail by comparing the influence of several factors including reactant, solvent, residence time, and feed concentration. The only successful approach to minimize fouling was the use of a polar aprotic solvent [dimethyl sulfoxide (DMSO)] with dilute (50 mM) reactant streams. In aqueous systems, operating the reactor in a regime with low conversion conditions (short residence times) does not significantly improve the longevity of the catalyst. Spent catalysts were characterized using C-13 solid-state NMR spectroscopy enhanced by dynamic nuclear polarization. Additionally, in situ H-1 and C-13 high-resolution magic angle spinning (HR-MAS) solid-state NMR spectroscopies were used to investigate the solvent influence at the catalyst interface. The HR-MAS NMR studies showed that in polar aprotic solvents, the increased acidity leads to greater selectivity toward HMF; more importantly, that the dehydration products do not readily adhere to the surface in DMSO, in contrast to their behavior in water. The results demonstrate that more active and longer-lived acid catalysts could be obtained by tuning the solvent and surface polarity to allow for efficient desorption of products, thereby reducing the catalyst deactivation that occurs due to fouling.


Synthetic Control Of The Photoluminescence Stability Of Organolead Halide Perovskites, Daniel J. Freppon, Long Men, Ujjal Bhattacharjee, Bryan A. Rosales, Feng Zhu, Jacob W. Petrich, Emily A. Smith, Javier Vela Oct 2019

Synthetic Control Of The Photoluminescence Stability Of Organolead Halide Perovskites, Daniel J. Freppon, Long Men, Ujjal Bhattacharjee, Bryan A. Rosales, Feng Zhu, Jacob W. Petrich, Emily A. Smith, Javier Vela

Chemistry Publications

An optimized synthetic procedure for preparing photostable nanocrystalline methylammonium lead halide materials is reported. The procedure was developed by adjusting the lead halide to methylammonium/octylammonium halide precursor ratio. At a high precursor ratio (1:3), a blue-shifted photoinduced luminescence peak is measured at 642 nm for CH3NH3PbI3 with 0.01 to 12 mJ pulsed-laser irradiation. The appearance of this peak is reversible over 300 min upon blocking the irradiation. In order to determine if the peak is the result of a phase change, in situ x-ray diffraction measurements were performed. No phase change was measured with an irradiance that ...


Diffraction Paradox: An Unusually Broad Diffraction Background Marks High Quality Graphene, Shen Chen, Michael Horn-Von Hoegen, Patricia A. Thiel, Michael C. Tringides Oct 2019

Diffraction Paradox: An Unusually Broad Diffraction Background Marks High Quality Graphene, Shen Chen, Michael Horn-Von Hoegen, Patricia A. Thiel, Michael C. Tringides

Chemistry Publications

The realization of the unusual properties of two-dimensional (2D) materials requires the formation of large domains of single-layer thickness, extending over the mesoscale. It is found that the formation of uniform graphene on SiC, contrary to textbook diffraction, is signaled by a strong bell-shaped component (BSC) around the (00) and G(10) spots (but not around the substrate spots). The BCS is also seen on graphene grown on metals, because a single uniform graphene layer can be also grown with large lateral size. It is only seen by electron diffraction but not with x-ray or He scattering. Although the origin ...


Investigating The Microstructure Of Poly(Cyclosilane) By 29si Solid-State Nmr Spectroscopy And Dft Calculations, Rick W. Dorn, Eric A. Marro, Michael P. Hanrahan, Rebekka S. Klausen, Aaron Rossini Oct 2019

Investigating The Microstructure Of Poly(Cyclosilane) By 29si Solid-State Nmr Spectroscopy And Dft Calculations, Rick W. Dorn, Eric A. Marro, Michael P. Hanrahan, Rebekka S. Klausen, Aaron Rossini

Chemistry Publications

Using high-resolution magic-angle spinning (MAS) solid-state NMR spectroscopy and density-functional theory (DFT) calculations, we determine the microstructure of the silicon-based functional polymer poly(1,4Si6) arising from the dehydrocoupling polymerization of cyclosilane 1,4Si6. 1H-29Si refocused-INEPT experiments allow the unambiguous determination of the number of attached protons to a silicon atom for each 29Si signal in 1,4Si6 and poly(1,4Si6). One-dimensional 1H→29Si cross-polarization MAS (CPMAS) spectra of poly(1,4Si6) show the development of SiH resonances upon polymerization and peak integration indicates an average degree of polymerization of 20. The 1H→29Si CPMAS spectrum of poly(1 ...


Synthesis And Characterization Of Silica-Supported Boron Oxide Catalysts For The Oxidative Dehydrogenation Of Propane, Alyssa M. Love, Melissa C. Cendejas, Brijith Thomas, William P. Mcdermott, Pajean Uchupalanun, Catherine Kruszynski, Samuel P. Burt, Theodore Agbi, Aaron Rossini, Ive Hermans Oct 2019

Synthesis And Characterization Of Silica-Supported Boron Oxide Catalysts For The Oxidative Dehydrogenation Of Propane, Alyssa M. Love, Melissa C. Cendejas, Brijith Thomas, William P. Mcdermott, Pajean Uchupalanun, Catherine Kruszynski, Samuel P. Burt, Theodore Agbi, Aaron Rossini, Ive Hermans

Chemistry Publications

In this contribution we report on the oxidative dehydrogenation (ODH) activity of silica-supported boron oxide prepared via incipient wetness impregnation. Characterization of pristine and spent catalysts with infrared, Raman, and solid-state NMR spectroscopy reveals the presence of both isolated and aggregated oxidized boron sites. The results of these investigations, in combination with our earlier work on bulk boron-containing ODH catalysts (e.g., h-BN, metal borides, and elemental boron), bolster the hypothesis that oxidized boron species in situ formed on the surface of these materials are responsible for the exceptional catalytic behavior. We anticipate that investigation of supported boron materials can ...


High Throughput Screening Of 3d Printable Resins: Adjusting The Surface And Catalytic Properties Of Multifunctional Architectures, J. Sebastián Manzano, Hsin Wang, Igor I. Slowing Sep 2019

High Throughput Screening Of 3d Printable Resins: Adjusting The Surface And Catalytic Properties Of Multifunctional Architectures, J. Sebastián Manzano, Hsin Wang, Igor I. Slowing

Chemistry Publications

Identification of 3D printable materials is crucial to expand the breadth of physical and chemical properties attainable by additive manufacturing. Stereolithography (SLA), a widespread 3D printing method based on resin photo-polymerization, is ideally suited for exploring a large variety of monomers to produce functional three-dimensional solids of diverse properties. However, for most of the commercially available SLA 3D printers, screening monomers and resin compositions requires large volumes (~150 mL) in each printing cycle, making the process costly and inefficient. Herein, a high throughput block (HTB) adaptor was developed to screen arrays of monomers and resin compositions, consuming lower volumes (< 2 mL) and less time per print (< 1/16 based on a 44 matrix) than using the original hardware. Using this approach, a library of materials with different surface hydrophobicities were 3D printed by including long chain acrylates in the resins. In addition, several metal salts were dissolved in an acrylic acid-based resin, 3D printed and screened as heterogeneous catalysts for the selective aerobic oxidation of benzyl alcohol to benzaldehyde. Cu(II)-based resins produced the most active structures. Combinations of Cu(II) and long chain acrylate monomers were then used to 3D print complex catalytic architectures with varying degrees of hydrophobicity. Linear relationships were observed between 3D printed surface area, surface hydrophobicity and catalyst performance. For a high surface Schwarz P topology ca. 60 % enhancement in the catalytic activity of Cu(II) was attained by replacing the parent resin with one containing hydrophobic isodecyl groups, indicating that the immediate environment of the catalytic site affected its performance. The HTB enables fast screening of resins for 3D printing multifunctional architectures with intrinsic catalytic activity, tunable surface properties, and minimal waste.


Probing The Surface Structure Of Semiconductor Nanoparticles By Dnp Sens With Dielectric Support Materials, Michael P. Hanrahan, Yunhua Chen, Rafael Blome-Fernández, Jennifer L. Stein, Gregory F. Pach, Marquix A. S. Adamson, Nathan R. Neale, Brandi M. Cossairt, Javier Vela, Aaron J. Rossini Aug 2019

Probing The Surface Structure Of Semiconductor Nanoparticles By Dnp Sens With Dielectric Support Materials, Michael P. Hanrahan, Yunhua Chen, Rafael Blome-Fernández, Jennifer L. Stein, Gregory F. Pach, Marquix A. S. Adamson, Nathan R. Neale, Brandi M. Cossairt, Javier Vela, Aaron J. Rossini

Chemistry Publications

Surface characterization is crucial for understanding how the atomic-level structure affects the chemical and photophysical properties of semiconducting nanoparticles (NPs). Solid-state nuclear magnetic resonance spectroscopy (NMR) is potentially a powerful technique for the characterization of the surface of NPs, but it is hindered by poor sensitivity. Dynamic nuclear polarization surface enhanced NMR spectroscopy (DNP SENS) has previously been demonstrated to enhance the sensitivity of surface-selective solid-state NMR experiments by one to two orders of magnitude. Established sample preparations for DNP SENS experiments on NPs require the dilution of the NPs on mesoporous silica. Using hexagonal boron nitride (h-BN) to disperse ...


Effect Of Structure On The Spin Switching And Magnetic Bistability Of Solid-State Aryl Dicyanomethyl Monoradicals And Diradicals, Joshua P. Peterson, Rui Zhang, Arthur H. Winter Aug 2019

Effect Of Structure On The Spin Switching And Magnetic Bistability Of Solid-State Aryl Dicyanomethyl Monoradicals And Diradicals, Joshua P. Peterson, Rui Zhang, Arthur H. Winter

Chemistry Publications

Stable organic radicals with switchable spin states have applications in medicine, biology, and material science. An emerging class of such spin-switchable radicals is based on dicyanomethyl radicals, which are typically thermally and air-stable species that form weakly bonded (closed-shell singlet) dimers at a lower temperature that rupture into electron paramagnetic resonance-active diradicals at a higher temperature. However, thus far, the study of these dicyanomethyl radicals has focused on their solution-phase behavior. An understanding of how chemical structure affects the solid-state spin switching behavior for these radicals is unknown. Here, we examine the solid-state spin crossover behavior of 6 monoradicals and ...