May 25, 2015

Just add lanthanides

  • Elizabeth Skovran and
  • Norma Cecilia Martinez-Gomez
Science 22 May 2015: 862-863.
Some methanol-using bacteria may depend on lanthanide elements for carbon capture and energy generation
A method to form carbon-nitrogen bonds via nitro group reduction could streamline synthetic routes in medicinal chemistry. [Also see Perspective by Kürti]

 The synthesis and functionalization of amines are fundamentally important in a vast range of chemical contexts. We present an amine synthesis that repurposes two simple feedstock building blocks: olefins and nitro(hetero)arenes. Using readily available reactants in an operationally simple procedure, the protocol smoothly yields secondary amines in a formal olefin hydroamination. Because of the presumed radical nature of the process, hindered amines can easily be accessed in a highly chemoselective transformation. A screen of more than 100 substrate combinations showcases tolerance of numerous unprotected functional groups such as alcohols, amines, and even boronic acids. This process is orthogonal to other aryl amine syntheses, such as the Buchwald-Hartwig, Ullmann, and classical amine-carbonyl reductive aminations, as it tolerates aryl halides and carbonyl compounds.


Streamlining amine synthesis

  • László Kürti
Science 22 May 2015: 863-864.
Bulky amine groups that help make many drugs more bioavailable can be added readily to organic compounds [Also see Research Article by Gui et al.]

Redox Non-innocent Ligand Controls Water Oxidation Overpotential in a New Family of Mononuclear Cu-Based Efficient Catalysts

Publication Date (Web): May 18, 2015 (Communication)
DOI: 10.1021/jacs.5b03977
Abstract Image
A new family of tetra-anionic tetradentate amidate ligands, N1,N1′-(1,2-phenylene)bis(N2-methyloxalamide) (H4L1), and its derivatives containing electron-donating groups at the aromatic ring have been prepared and characterized, together with their corresponding anionic Cu(II) complexes, [(LY)Cu]2–. At pH 11.5, the latter undergoes a reversible metal-based III/II oxidation process at 0.56 V and a ligand-based pH-dependent electron-transfer process at 1.25 V, associated with a large electrocatalytic water oxidation wave (overpotential of 700 mV). Foot-of-the-wave analysis gives a catalytic rate constant of 3.6 s–1 at pH 11.5 and 12 s–1 at pH 12.5. As the electron-donating capacity at the aromatic ring increases, the overpotential is drastically reduced down to a record low of 170 mV. In addition, DFT calculations allow us to propose a complete catalytic cycle that uncovers an unprecedented pathway in which crucial O–O bond formation occurs in a two-step, one-electron process where the peroxo intermediate generated has no formal M–O bond but is strongly hydrogen bonded to the auxiliary ligand.

Proton-Coupled Electron Transfer Constitutes the Photoactivation Mechanism of the Plant Photoreceptor UVR8

Publication Date (Web): May 8, 2015 (Article)
DOI: 10.1021/jacs.5b01177
Abstract Image
UVR8 is a novel UV-B photoreceptor that regulates a range of plant responses and is already used as a versatile optogenetic tool. Instead of an exogenous chromophore, UVR8 uniquely employs tryptophan side chains to accomplish UV-B photoreception. UV-B absorption by homodimeric UVR8 induces monomerization and hence signaling, but the underlying photodynamic mechanisms are not known. Here, by using a combination of time-resolved fluorescence and absorption spectroscopy from femto- to microseconds, we provide the first experimental evidence for the UVR8 molecular signaling mechanism. The results indicate that tryptophan residues at the dimer interface engage in photoinduced proton coupled electron transfer reactions that induce monomerization.

May 20, 2015

Efficient Removal of Organic Ligands from Supported Nanocrystals by Fast Thermal Annealing Enables Catalytic Studies on Well-Defined Active Phases

Publication Date (Web): May 11, 2015 (Article)
DOI: 10.1021/jacs.5b03333
Abstract Image
A simple yet efficient method to remove organic ligands from supported nanocrystals is reported for activating uniform catalysts prepared by colloidal synthesis procedures. The method relies on a fast thermal treatment in which ligands are quickly removed in air, before sintering can cause changes in the size and shape of the supported nanocrystals. A short treatment at high temperatures is found to be sufficient for activating the systems for catalytic reactions. We show that this method is widely applicable to nanostructures of different sizes, shapes, and compositions. Being rapid and effective, this procedure allows the production of monodisperse heterogeneous catalysts for studying a variety of structure–activity relationships. We show here results on methane steam reforming, where the particle size controls the CO/CO2 ratio on alumina-supported Pd, demonstrating the potential applications of the method in catalysis.

Illuminating CO2 reduction on frustrated Lewis pair surfaces: investigating the role of surface hydroxides and oxygen vacancies on nanocrystalline In2O3−x(OH)y

Phys. Chem. Chem. Phys., 2015, Advance Article

DOI: 10.1039/C5CP02613J
Designing catalytic nanostructures that can thermochemically or photochemically convert gaseous carbon dioxide into carbon based fuels is a significant challenge which requires a keen understanding of the chemistry of reactants, intermediates and products on surfaces. In this context, it has recently been reported that the reverse water gas shift reaction (RWGS), whereby carbon dioxide is reduced to carbon monoxide and water, CO2 + H2 → CO + H2O, can be catalysed by hydroxylated indium oxide nanocrystals, denoted In2O3−x(OH)y, more readily in the light than in the dark. The surface hydroxide groups and oxygen vacancies on In2O3−x(OH)y were both shown to assist this reaction. While this advance provides a first step toward the rational design and optimization of a single-component gas-phase CO2 reduction catalyst for solar fuels generation, the precise role of the hydroxide groups and oxygen vacancies in facilitating the reaction on In2O3−x(OH)y nanocrystals has not been resolved. In the work reported herein, for the first time we present in situ spectroscopic and kinetic observations, complemented by density functional theory analysis, that together provide mechanistic information into the surface reaction chemistry responsible for the thermochemical and photochemical RWGS reaction. Specifically, we demonstrate photochemical CO2 reduction at a rate of 150 μmol gcat−1 hour−1, which is four times better than the reduction rate in the dark, and propose a reaction mechanism whereby a surface active site of In2O3−x(OH)y, composed of a Lewis base hydroxide adjacent to a Lewis acid indium, together with an oxygen vacancy, assists the adsorption and heterolytic dissociation of H2 that enables the adsorption and reaction of CO2 to form CO and H2O as products. This mechanism, which has its analogue in molecular frustrated Lewis pair (FLP) chemistry and catalysis of CO2and H2, is supported by preliminary kinetic investigations. The results of this study emphasize the importance of engineering the surfaces of nanostructures to facilitate gas-phase thermochemical and photochemical carbon dioxide reduction reactions to energy rich fuels at technologically significant rates.

Graphical abstract: Illuminating CO2 reduction on frustrated Lewis pair surfaces: investigating the role of surface hydroxides and oxygen vacancies on nanocrystalline In2O3−x(OH)y

May 19, 2015

Applying green chemistry to the photochemical route to artemisinin

Zacharias Amara, Jessica F. B. Bellamy, Raphael Horvath, Samuel J. Miller, Andrew Beeby, Andreas Burgard, Kai Rossen, Martyn Poliakoff & Michael W. George

Nature Chemistry (2015) doi:10.1038/nchem.2261
Published online 11 May 2015

Artemisinin is an important antimalarial drug, but, at present, the environmental and economic costs of its semi-synthetic production are relatively high. Most of these costs lie in the final chemical steps, which follow a complex acid- and photo-catalysed route with oxygenation by both singlet and triplet oxygen. We demonstrate that applying the principles of green chemistry can lead to innovative strategies that avoid many of the problems in current photochemical processes. The first strategy combines the use of liquid CO2 as solvent and a dual-function solid acid/photocatalyst. The second strategy is an ambient-temperature reaction in aqueous mixtures of organic solvents, where the only inputs are dihydroartemisinic acid, O2 and light, and the output is pure, crystalline artemisinin. Everything else—solvents, photocatalyst and aqueous acid—can be recycled. Some aspects developed here through green chemistry are likely to have wider application in photochemistry and other reactions.

May 18, 2015

Saved: Electronic Structure of IrO2: The Role of the Metal d Orbitals

Electronic Structure of IrO2: The Role of the Metal d Orbitals by Yuan Ping, Giulia Galli and William A. Goddard via The Journal of Physical Chemistry C: Latest Articles (ACS Publications)

Saved: Fe/N/C Electrocatalysts for Oxygen Reduction Reaction in PEM Fuel Cells Using Nitrogen-Rich Ligand as Precursor

Fe/N/C Electrocatalysts for Oxygen Reduction Reaction in PEM Fuel Cells Using Nitrogen-Rich Ligand as Precursor by Lingling Yang, Yumiao Su, Wenmu Li and Xianwen Kan via The Journal of Physical Chemistry C: Latest Articles (ACS Publications)

Saved: Control of Methylene Blue Photo-Oxidation Rate over Polycrystalline Anatase TiO2 Thin Films via Carrier Concentration

Control of Methylene Blue Photo-Oxidation Rate over Polycrystalline Anatase TiO2 Thin Films via Carrier Concentration by S. W. Daniel Ong, Jianyi Lin and Edmund G. Seebauer via The Journal of Physical Chemistry C: Latest Articles (ACS Publications)

Saved: Alkaline Electrolyte and Fe Impurity Effects on the Performance and Active-Phase Structure of NiOOH Thin Films for OER Catalysis Applications

Alkaline Electrolyte and Fe Impurity Effects on the Performance and Active-Phase Structure of NiOOH Thin Films for OER Catalysis Applications by John D. Michael, Ethan L. Demeter, Steven M. Illes, Qingqi Fan, Jacob R. Boes and John R. Kitchin via The Journal of Physical Chemistry C: Latest Articles (ACS Publications)

Morphological Features and Band Bending at Nonpolar Surfaces of ZnO

Morphological Features and Band Bending at Nonpolar Surfaces of ZnO by David Mora-Fonz, John Buckeridge, Andrew J. Logsdail, David O. Scanlon, Alexey A. Sokol, Scott Woodley and C. Richard A. Catlow via The Journal of Physical Chemistry C: Latest Articles (ACS Publications)
Publication Date (Web): May 15, 2015 (Article)
DOI: 10.1021/ja512482n


Abstract Image
Development of better catalysts for the oxygen reduction reaction (ORR) and other electrocatalytic processes requires detailed knowledge of reaction pathways and intermediate species. Here we report a new methodology for detecting charged reactive intermediates and its application to the mechanistic analysis of ORR. A nanopipette filled with an organic phase that is immiscible with the external aqueous solution was used as a tip in the scanning electrochemical microscope to detect and identify a short-lived superoxide (O2●–) intermediate and to determine the rate of its generation at the catalytic Pt substrate and its lifetime in neutral aqueous solution. The voltammogram of the O2●– anion transfer to the organic phase provides a unique signature for unambiguous identification of superoxide. The extremely short attainable separation distance between the pipette tip and substrate surface (∼1 nm) makes this technique suitable for detecting and identifying charged intermediates of catalytic processes with a lifetime of a few nanoseconds.

May 15, 2015

Rate Law Analysis of Water Oxidation on a Hematite Surface

Department of Chemistry, Imperial College London, South Kensington Campus, London, SW7 2AZ, United Kingdom
Institut des Sciences et Ingénierie Chimiques, Laboratory of Photonics and Interfaces, Ecole Polytechnique Fédérale de Lausanne, Station 6, CH-1015 Lausanne, Switzerland
J. Am. Chem. Soc., Article ASAP
DOI: 10.1021/jacs.5b02576
Publication Date (Web): May 2, 2015
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Water oxidation is a key chemical reaction, central to both biological photosynthesis and artificial solar fuel synthesis strategies. Despite recent progress on the structure of the natural catalytic site, and on inorganic catalyst function, determining the mechanistic details of this multiredox reaction remains a significant challenge. We report herein a rate law analysis of the order of water oxidation as a function of surface hole density on a hematite photoanode employing photoinduced absorption spectroscopy. Our study reveals a transition from a slow, first order reaction at low accumulated hole density to a faster, third order mechanism once the surface hole density is sufficient to enable the oxidation of nearest neighbor metal atoms. This study thus provides direct evidence for the multihole catalysis of water oxidation by hematite, and demonstrates the hole accumulation level required to achieve this, leading to key insights both for reaction mechanism and strategies to enhance function.

Steric Effects on the Primary Isotope Dependence of Secondary Kinetic Isotope Effects in Hydride Transfer Reactions in Solution: Caused by the Isotopically Different Tunneling Ready State Conformations?

Department of Chemistry, Southern Illinois University Edwardsville, Edwardsville, Illinois 62026, United States
J. Am. Chem. Soc., Article ASAP
DOI: 10.1021/jacs.5b03085
Publication Date (Web): May 5, 2015
Abstract Image
The observed 1° isotope effect on 2° KIEs in H-transfer reactions has recently been explained on the basis of a H-tunneling mechanism that uses the concept that the tunneling of a heavier isotope requires a shorter donor–acceptor distance (DAD) than that of a lighter isotope. The shorter DAD in D-tunneling, as compared to H-tunneling, could bring about significant spatial crowding effect that stiffens the 2° H/D vibrations, thus decreasing the 2° KIE. This leads to a new physical organic research direction that examines how structure affects the 1° isotope dependence of 2° KIEs and how this dependence provides information about the structure of the tunneling ready states (TRSs). The hypothesis is that H- and D-tunneling have TRS structures which have different DADs, and pronounced 1° isotope effect on 2° KIEs should be observed in tunneling systems that are sterically hindered. This paper investigates the hypothesis by determining the 1° isotope effect on α- and β-2° KIEs for hydride transfer reactions from various hydride donors to different carbocationic hydride acceptors in solution. The systems were designed to include the interactions of the steric groups and the targeted 2° H/D’s in the TRSs. The results substantiate our hypothesis, and they are not consistent with the traditional model of H-tunneling and 1°/2° H coupled motions that has been widely used to explain the 1° isotope dependence of 2° KIEs in the enzyme-catalyzed H-transfer reactions. The behaviors of the 1° isotope dependence of 2° KIEs in solution are compared to those with alcohol dehydrogenases, and sources of the observed “puzzling” 2° KIE behaviors in these enzymes are discussed using the concept of the isotopically different TRS conformations.

Establishing the Hydride Donor Abilities of Main Group Hydrides LINK 

Department of Chemistry, Washington State University, Pullman, Washington 99164, United States
Organometallics, Article ASAP
DOI: 10.1021/om5011512
Publication Date (Web): May 6, 2015
Abstract Image 
ABSTRACT: Interest in reductions with main group hydrides has been reinvigorated with the discovery of frustrated Lewis pairs. Computational analysis showed that the borohydride of the commonly used Lewis acid B(C6F5)3 was determined to be 15 kcal/mol less reducing than borohydride ([BH4]), 22 kcal/mol less reducing than aluminum hydride ([AlH4]), and 41 kcal/mol less reducing than superhydride ([HBEt3]). In addition to [HB(C6F5)3], a hydride donor ability scale with an estimated error of ∼3 kcal/mol includes 132 main group hydrides with gradually changing reducing capabilities spanning 160 kcal/mol. The scale includes representatives from organosilanes, organogermanes, organostannanes, borohydrides, boranes, aluminum hydrides, NADH analogues, and CH hydride donors. The large variety of reducing agents and the wide span of the scale (ranging from 0.5 to 160 kcal/mol in acetonitrile) make the scale a useful tool for the future design of metal-based or main group reducing agents.

Iridium Nanocrystal Synthesis and Surface Coating-Dependent Catalytic Activity

Discusses how capping group identity and density influences reactivity of MOx

Iridium Nanocrystal Synthesis and Surface Coating-Dependent Catalytic Activity

Department of Chemical Engineering, Texas Materials Institute and Center for Nano and Molecular Science and Technology, The University of Texas, Austin, Texas 78712-1062
Nano Lett., 2005, 5 (7), pp 1203–1207
DOI: 10.1021/nl050648f
Publication Date (Web): June 2, 2005
Copyright © 2005 American Chemical Society


Abstract Image
Iridium (Ir) nanocrystals were synthesized by reducing (methylcyclopentadienyl)(1,5-cyclooctadiene)Ir with hexadecanediol in the presence of four different capping ligand combinations:  oleic acid and oleylamine, trioctylphosphine (TOP), tetraoctylammonium bromide (TOAB), and tetraoctylphosphonium bromide (TOPB). The oleic acid/oleylamine-capped nanocrystals were of the highest quality, with the narrowest size and shape distribution. The Ir nanocrystals were tested for their ability to catalyze the hydrogenation of 1-decene as a model reaction. The oleic acid/oleylamine and TOP-capped nanocrystals were both catalytically dead. TOAB and TOPB-coated nanocrystals both catalyzed 1-decene hydrogenation, with the TOPB-coated nanocrystals exhibiting the highest turnover frequencies. Recycling through several catalytic reactions increased the catalytic activity, presumably as a result of ligand desorption and increased exposure of the metal surface, with ligand desorption eventually leading to precipitation and significantly decreased activity.

May 14, 2015

The Reaction Mechanism with Free Energy Barriers for Electrochemical Dihydrogen Evolution on MoS2

Publication Date (Web): May 5, 2015 (Article)
DOI: 10.1021/jacs.5b03329
Abstract Image
We report density functional theory (M06L) calculations including Poisson–Boltzmann solvation to determine the reaction pathways and barriers for the hydrogen evolution reaction (HER) on MoS2, using both a periodic two-dimensional slab and a Mo10S21 cluster model. We find that the HER mechanism involves protonation of the electron rich molybdenum hydride site (Volmer–Heyrovsky mechanism), leading to a calculated free energy barrier of 17.9 kcal/mol, in good agreement with the barrier of 19.9 kcal/mol estimated from the experimental turnover frequency. Hydronium protonation of the hydride on the Mo site is 21.3 kcal/mol more favorable than protonation of the hydrogen on the S site because the electrons localized on the Mo–H bond are readily transferred to form dihydrogen with hydronium. We predict the Volmer–Tafel mechanism in which hydrogen atoms bound to molybdenum and sulfur sites recombine to form H2 has a barrier of 22.6 kcal/mol. Starting with hydrogen atoms on adjacent sulfur atoms, the Volmer–Tafel mechanism goes instead through the M–H + S–H pathway. In discussions of metal chalcogenide HER catalysis, the S–H bond energy has been proposed as the critical parameter. However, we find that the sulfur–hydrogen species is not an important intermediate since the free energy of this species does not play a direct role in determining the effective activation barrier. Rather we suggest that the kinetic barrier should be used as a descriptor for reactivity, rather than the equilibrium thermodynamics. This is supported by the agreement between the calculated barrier and the experimental turnover frequency. These results suggest that to design a more reactive catalyst from edge exposed MoS2, one should focus on lowering the reaction barrier between the metal hydride and a proton from the hydronium in solution.

Spin-Reconstructed Proton-Coupled Electron Transfer in a Ferrocene–Nickeladithiolene Hybrid

Publication Date (Web): May 14, 2015 (Communication)
DOI: 10.1021/jacs.5b02118
Abstract Image
A proton–electron dual-responsive system based on a hybrid of ferrocene and metalladithiolene (1) was developed. The formation of the dithiafulvenium moiety was driven by protonation of the metalladithiolene unit of 1 and by oxidation. The change in the electronic structure caused by the protonation was combined with the redox properties of the two components of 1, generating two radical species with different spin density distributions (3d spin and π spin). Furthermore, a spin-reconstructed proton-coupled electron transfer, i.e., the transformation from 3d spin to π spin accompanied by deprotonation, was achieved by a temperature change, the third external stimulus.

May 11, 2015

Unimolecular Electronics

Laboratory for Molecular Electronics, Department of Chemistry, The University of Alabama, Box 870336, Tuscaloosa, Alabama 35487-0336, United States
Chem. Rev., Article ASAP
DOI: 10.1021/cr500459d
Publication Date (Web): May 7, 2015
Copyright © 2015 American Chemical Society

Table of Contents:
  • 1. Introduction
  • 2. Summary of Significant Results
  • 3. Contacts from Molecule to Metal and Energy Level Shifts
  • 4. Marcus Theory of Electron Transfer within a Molecule
  • 5. Electrical Conductivity, Classical and Quantized: Ohm’s Law and Tunneling
  • 6. WKBJ or Quasi-classical Method
  • 7. Fowler–Nordheim equation
  • 8. Simmons Equation
  • 9. Newns–Anderson Equation and Eigenvalue Staircase
  • 10. Other Tunneling Regimes
  • 11. Landauer Equation
  • 12. Two-Probe Conductivity Measurement Techniques
  • 13. Thermopower
  • 14. Coulomb Blockade, Coulomb Staircase, and Coulomb Diamonds
  • 15. Negative Differential Resistance and Potential Power Gain with Two-Probe Methods
  • 16. Gating in Field-Effect Transistors and in Molecular Conductance
  • 17. Spintronics
  • 18. Conductivity of Molecular Wires
  • 19. Transition Voltage Spectroscopy
  • 20. Asymmetries in IV Curves: Rectification
  • 21. Rectifier or Diode: What Is in a Name?
  • 22. Three Mechanisms for Rectification by Molecules
  • 23. Unimolecular Rectification by One Level: Schottky Barrier Rectifiers (S)
  • 24. Unimolecular Rectification (U by One or Two Levels)
  • 25. Rectification in Macroscopic Films and Langmuir–Blodgett Multilayers
  • 26. A and S Rectification by Resonance with Only One Molecular Energy Level
  • 27. Monolayer Photodiode and Electrochemical Rectification
  • 28. Rectification To Help Artificial Photosynthesis
  • 29. Inelastic Electron Tunneling Spectroscopy Orbital-Mediated Tunneling and STM
  • 30. Unimolecular Amplifier
  • 31. DNA Conductivity, Complementarity, And Origami
  • 32. Conclusion

Metal-Free Catalysts for Oxygen Reduction Reaction

Center of Advanced Science and Engineering for Carbon (Case4Carbon), Department of Macromolecular Science and Engineering, Case Western Reserve University, 10900 Euclid Avenue, Cleveland, Ohio 44106, United States
§ Key Laboratory of Cluster Science, Ministry of Education of China, Beijing Key Laboratory of Photoelectronic/Electrophotonic Conversion Materials, Department of Chemistry, School of Science, Beijing Institute of Technology, Beijing 100081, People’s Republic of China
School of Energy and Chemical Engineering/Center for Dimension-Controllable Covalent Organic Frameworks, Ulsan National Institute of Science and Technology (UNIST), 100 Banyeon, Ulsan, 689-798, South Korea
Chem. Rev., Article ASAP
DOI: 10.1021/cr5003563
Publication Date (Web): May 4, 2015
Copyright © 2015 American Chemical Society
Table of Contents:
  • 1. Introduction
  • 2. Carbon Nanomaterials
    • 2.1. Fullerenes
    • 2.2. Carbon Nanotubes
    • 2.3. Graphene
    • 2.4. Nanostructured Graphite and Nanodiamond
    • 2.5. Heteroatom-Doped Carbon Nanomaterials
      • 2.5.1. Nitrogen-Doped Fullerenes, CNTs, Graphene, and Graphite
      • 2.5.2. Carbon Nanomaterials Doped with Heteroatoms Other than Nitrogen
      • 2.5.3. BCN Nanotubes and Graphene
  • 3. Oxygen Reduction Reaction (ORR)
    • 3.1. Two-Electron and Four-Electron ORR Processes
      • 3.1.1. Metal-Based Catalysts for ORR
      • 3.1.2. Metal-Based Catalysts Supported by Carbon Nanomaterials for ORR
      • 3.1.3. Metal–Nitrogen–Carbon (M–N–C) Nonprecious Metal Catalysts
  • 4. Metal-Free ORR Catalysts
    • 4.1. Intramolecular Charge Transfer
      • 4.1.1. Carbon Nanotubes as Metal-Free Catalysts
      • 4.1.2. Graphene as Metal-Free Catalysts
      • 4.1.3. Graphite as Metal-Free Catalysts
      • 4.1.4. Carbon-Nitride-Based Materials as Metal-Free Catalysts
      • 4.1.5. Three-Dimensional (3D) Carbon Nanomaterials as Metal-Free Catalysts
    • 4.2. Intermolecular Charge Transfer
    • 4.3. Spin Redistribution
    • 4.4. Heteroatom-Doped Carbon Nanomaterials as Metal-Free ORR Catalysts in Acids
    • 4.5. Heteroatom-Doped Carbon Nanomaterials as Bi-/Multi-functional Metal-Free Catalysts
      • 4.5.1. Bifunctional Metal-Free Catalysts for ORR/OER
      • 4.5.2. Bifunctional Metal-Free Catalysts for OER/HER
    • 4.6. Performance Evaluation for Heteroatom-Doped Carbon ORR Catalysts in Fuel Cells
  • 5. Concluding Remarks

Organic–Inorganic Hybrid Nanocomposite-Based Gas Sensors for Environmental Monitoring

Center for Personalized Nanomedicine, Institute of Neuroimmune Pharmacology, Department of Immunology, Herbert Wertheim College of Medicine, Florida International University, Miami, Florida 33199, United States
Bio-MEMS Microsystems Laboratory, Department of Electrical and Computer Engineering, College of Engineering, Florida International University, Miami, Florida 33174, United States
§ Department of Physics, Panjab University, Chandigarh 160014, India
Bioelectronics Program, Institute of Microelectronics, A*Star, 11 Science Park Road, Singapore Science Park II, Singapore
Department of Biotechnology, Delhi Technological University, Shahbad Daulatpur, Delhi 110042, India
Chem. Rev., Article ASAP
DOI: 10.1021/cr400659h
Publication Date (Web): May 1, 2015
Copyright © 2015 American Chemical Society
Table of Contents:
  • 1. Introduction
  • 2. Organic–Inorganic Hybrid Nanocomposites: Smart Advanced Functionalzed Materials for Gas Sensing
    • 2.1. Preparation Methods of Organic–Inorganic Nanocomposites
  • 3. Gas Sensing Principle of Organic–Inorganic Hybrid Nanocomposites
  • 4. Organic–Inorganic Hybrid Nanocomposite-Based Gas Sensors for Environmental Monitoring
    • 4.1. Organic–Inorganic Hybrid Nanocomposites for Volatile Organic Compounds (VOCs)
    • 4.2. Organic–Inorganic Hybrid Nanocomposites for Hydrochloric Acid (HCl) Detection
    • 4.3. Organic–Inorganic Hybrid Nanocomposites for Ammonia (NH3) Detection
    • 4.4. Organic–Inorganic Hybrid Nanocomposites for Hydrogen Disulfide (H2S) Detection
    • 4.5. Organic–Inorganic Hybrid Nanocomposites for Detection of Nitrogen Oxides (NOx)
    • 4.6. Organic–Inorganic Hybrid Nanocomposites for Carbon Dioxide (CO2) Detection
    • 4.7. Organic–Inorganic Hybrid Nanocomposites for Carbon Monoxide (CO) Detection
  • 5. Organic–Inorganic Hybrid Nanocomposites for Humidity Detection
  • 6. Challenges in Organic–Inorgnic Hybrid Nanocomposite-Based Gas Sensing
  • 7. Conclusions

Saturation Vapor Pressures and Transition Enthalpies of Low-Volatility Organic Molecules of Atmospheric Relevance: From Dicarboxylic Acids to Complex Mixtures

Department of Chemistry, Aarhus University, DK-8000 Aarhus, Denmark
Department of Civil and Environmental Engineering, Portland State University, Portland, Oregon 97207, United States
§Centre for Atmospheric Science, School of Earth, Atmospheric and Environmental Sciences, and National Centre for Atmospheric Science (NCAS), University of Manchester, Manchester M13 9PL, United Kingdom
Department of Civil and Environmental Engineering and #Air Quality Research Center, University of California, Davis, California 95616, United States
Centre for Atmospheric Particle Studies, Carnegie Mellon University, Pittsburgh, Pennsylvania 15213, United States
Institute for Atmospheric and Climate Science, ETH Zurich, 8092 Zurich, Switzerland
Marcolli Chemistry and Physics Consulting GmbH, 8047 Zurich, Switzerland
Department of Chemistry and Biochemistry and Cooperative Institute for Research in Environmental Sciences (CIRES), University of Colorado, Boulder, Colorado 80309, United States
School of Environmental Sciences, University of East Anglia, Norwich NR4 7TJ, United Kingdom
School of Chemistry, University of Bristol, Bristol BS8 1TH, United Kingdom
Atmospheric Science, Department of Chemistry and Molecular Biology, University of Gothenburg, SE-405 30 Gothenburg, Sweden
IVL Swedish Environmental Research Institute, SE-411 33 Gothenburg, Sweden
Division of Atmospheric Sciences, Desert Research Institute, Reno, Nevada 89512, United States
Department of Physics, University of Helsinki, FI-00014 Helsinki, Finland
School of Geography, Earth and Environmental Sciences, University of Birmingham, Birmingham B15 2TT, United Kingdom
Centro de Investigação em Química, Department of Chemistry and Biochemistry, Faculty of Science, University of Porto, 4099-002 Porto, Portugal
Department of Chemistry, University of Copenhagen, DK-1165 Copenhagen, Denmark
Maritime Environment, Shipping and Marine Technology, Chalmers University of Technology, SE-412 96 Gothenburg, Sweden
Center of Excellence on Hazardous Substance Management, Chulalongkorn University, Bangkok 10330, Thailand
Department of Applied Physics, University of Eastern Finland, FI-70211 Kuopio, Finland
Ergonomics & Aerosol Technology, Lund University, SE-221 00 Lund, Sweden
School of Chemical Engineering, University of KwaZulu-Natal, Durban 4041, South Africa
DDBST GmbH, D-26129 Oldenburg, Germany
Industrial Chemistry, Carl von Ossietzky University Oldenburg, D-26129 Oldenburg, Germany
European Commission Joint Research Centre (JRC), Institute for Energy and Transport, Sustainable Transport Unit, I-21027 Ispra, Italy
Department of Environmental Science and Analytical Chemistry (ACES) and Bolin Centre for Climate Research, Stockholm University, SE-106 91 Stockholm, Sweden
Chem. Rev., Article ASAP
DOI: 10.1021/cr5005502
Publication Date (Web): May 1, 2015
Copyright © 2015 American Chemical Society

Table of Contents:
  • 1. Introduction
  • 2. Theoretical Background and Framework for Atmospheric Aerosols
    • 2.1. Saturation Vapor Pressures
    • 2.2. Vapor–Liquid or Vapor–Solid Equilibria over Mixed Solutions
    • 2.3. Equilibria over Curved Surfaces
    • 2.4. Dynamic Evaporation and Condensation from and to an Aerosol Particle
    • 2.5. Ambient Partitioning
  • 3. Experimental Methods
    • 3.1. Knudsen-Cell-Based Methods
      • 3.1.1. Knudsen Mass Loss Methods
      • 3.1.2. Knudsen Effusion Mass Spectrometry
    • 3.2. Single-Particle Methods
      • 3.2.1. Electrodynamic Balance
      • 3.2.2. Optical Tweezers
    • 3.3. Particle Size Distribution Methods
      • 3.3.1. Flow Tube Tandem Differential Mobility Analyzer
      • 3.3.2. Volatility Tandem Differential Mobility Analyzer
      • 3.3.3. Integrated Volume Method
    • 3.4. Thermal Desorption Methods
      • 3.4.1. Thermal Desorption Particle Beam Mass Spectrometry
      • 3.4.2. Temperature-Programmed Desorption Proton Transfer Chemical Ionization Mass Spectrometry
      • 3.4.3. Atmospheric Solids Analysis Probe Mass Spectrometry
  • 4. Experimentally Determined Saturation Vapor Pressures and Transition Enthalpies of Dicarboxylic Acids
    • 4.1. Straight-Chain Dicarboxylic Acids
      • 4.1.1. General Fitting Procedure
      • 4.1.2. Oxalic Acid (C2H2O4)
      • 4.1.3. Malonic Acid (C3H4O4)
      • 4.1.4. Succinic Acid (C4H6O4)
      • 4.1.5. Glutaric Acid (C5H8O4)
      • 4.1.6. Adipic Acid (C6H10O4)
      • 4.1.7. Pimelic Acid (C7H12O4)
      • 4.1.8. C8–C10 Acids
    • 4.2. Conclusions on Straight-Chain Dicarboxylic Acids
    • 4.3. Related Dicarboxylic Acids
      • 4.3.1. Solid-State Saturation Vapor Pressures
      • 4.3.2. Subcooled-Liquid-State Saturation Vapor Pressures
  • 5. Saturation Vapor Pressure Estimation Methods
    • 5.1. Group Contribution Methods
      • 5.1.1. Temperature-Dependent GCMs Requiring a Boiling Point
      • 5.1.2. Temperature-Dependent GCMs Not Requiring a Boiling Point
      • 5.1.3. Application and Assessment of GCMs for Dicarboxylic Acids
    • 5.2. Pure-Component Sensitivity Studies
      • 5.2.1. Recommendations Based on Pure-Component Studies
  • 6. Well-Defined Mixtures Containing Dicarboxylic Acids
    • 6.1. Mixtures of Dicarboxylic Acids with Water and Common Inorganic Aerosol Constituents
    • 6.2. Mixtures of Multiple Dicarboxylic Acids
  • 7. Bridging the Gap between Saturation Vapor Pressures of Individual Organic Molecules and Atmospheric Aerosol Volatility
    • 7.1. Bottom-Up Methods: Explicit Prediction of Secondary Organic Aerosol Partitioning
    • 7.2. Molecular Probes of Physical-Chemical Properties of Complex Organic Aerosols
    • 7.3. Top-Down Methods: Volatility Distributions of Complex Organic Mixtures and Atmospheric Impact
      • 7.3.1. Empirical Determination of Volatility Distributions of Complex Aerosols
  • 8. Summary and Conclusion

Kinetic Monte Carlo Simulation of Statistical Mechanical Models and Coarse-Grained Mesoscale Descriptions of Catalytic Reaction–Diffusion Processes: 1D Nanoporous and 2D Surface Systems

Ames Laboratory—USDOE, Division of Chemical and Biological Sciences, Department of Physics & Astronomy, and §Department of Mathematics, Iowa State University, Ames, Iowa 50011, United States
Chem. Rev., Article ASAP
DOI: 10.1021/cr500453t
Publication Date (Web): April 24, 2015
Copyright © 2015 American Chemical Society
Table of Contents:
  • 1. Introduction
  • 2. Catalytic Reaction–Diffusion Systems and Spatially Discrete Stochastic Models
    • 2.1. Catalytic Conversion Reactions in 1D Nanoporous Materials
    • 2.2. From Spatially Continuous to Discrete Stochastic Models for Reactions in 1D Nanoporous Materials
    • 2.3. Catalytic Reactions on 2D Metal Surfaces (Low to Moderate Pressure, P)
    • 2.4. Stochastic Multisite Lattice-Gas Models for 2D Surface Reactions (Low P)
      • 2.4.1. Thermodynamic Parameters
      • 2.4.2. Local Environment Dependence of Activation Barriers for Key Processes
      • 2.4.3. Complex Adsorption Dynamics and Concerted Mechanisms
      • 2.4.4. KMC Simulation Algorithms for Surface Reaction Models for Low P(7, 22)
    • 2.5. Reactions on 2D Oxide Surfaces (High P) and msLG Models
  • 3. Basic Formalism for Spatially Discrete Stochastic Models and Coarse-Graining to Continuum (Hydrodynamic) Reaction–Diffusion Equations
    • 3.1. Discrete Hierarchical Reaction–Diffusion Equations
    • 3.2. Hierarchical Truncation at the Mean-Field Level
    • 3.3. Higher-Order Hierarchical Truncation and Conditional Probabilities
    • 3.4. Coarse-Graining: Hydrodynamic Regime and Generalizations
    • 3.5. Onsager Formulation for Chemical Diffusion in Mixed Systems
  • 4. Basic Irreversible First-Order Conversion Reactions in 1D Linear Nanopores
    • 4.1. Exact Behavior vs Mean-Field and Hydrodynamic Treatments
    • 4.2. Formulation of Generalized Tracer Diffusivity Dtr(n)
    • 4.3. Further Discussion of Generalized Tracer Diffusivity Dtr(n)
    • 4.4. Generalized Hydrodynamic Formulation and Analysis
    • 4.5. Detailed Analysis of Spatial Correlations for Single-File Diffusion (SFD)
  • 5. General Conversion Reactions in 1D Linear Nanopores
    • 5.1. Nonuniform Distributions of Catalytic Sites
    • 5.2. Interactions between Reactant and Product Species
    • 5.3. Reactivity versus Conversion F ≥ 0 for Reversible Reactions
    • 5.4. Controlling Reactivity by Tuning Reaction Product–Pore Interior Interactions
    • 5.5. Concentration-Dependent First-Order Conversion Reactions
    • 5.6. Second-Order Bimolecular Conversion Reactions
    • 5.7. Unequal Mobility of Reactants and Products
  • 6. Realistic msLG Modeling of Catalytic Reactions on 2D fcc Metal Surfaces
    • 6.1. Prelude: LG and msLG Modeling for Chemisorbed Adlayers
    • 6.2. msLG Model for CO-oxidation on Metal (100) Surfaces
      • 6.2.1. CO Adsorption
      • 6.2.2. O2 Adsorption
      • 6.2.3. CO Desorption
      • 6.2.4. Diffusion of CO and O
      • 6.2.5. CO + O Reaction
    • 6.3. KMC Simulation Results for CO-oxidation on Pd(100) and Pt(100)
    • 6.4. msLG Models for CO-oxidation on Metal(111) Surfaces
    • 6.5. KMC Simulation Results for CO-oxidation on Pt(111) and Pd(111)
    • 6.6. Other Reactions: NO-oxidation and Decomposition, Hydrogenation, etc
  • 7. Tailored Models for CO-oxidation on Metal (100) Surfaces
    • 7.1. Development of a Basic Model for CO + O on Pd(100) at Low P
      • 7.1.1. Oxygen Sticking on Pure O Adlayers
      • 7.1.2. Oxygen Sticking for Mixed Adlayers (8 Blocking CO)
      • 7.1.3. Oxygen Sticking for Mixed Adlayers (10 Blocking CO)
      • 7.1.4. CO Sticking
      • 7.1.5. CO Desorption and CO + O Reaction
      • 7.1.6. Surface Diffusion
    • 7.2. Results for Basic Model for Low-P Bistability in CO + O on Pd(100)
    • 7.3. Refined Model with Reactive Phase Separation for CO + O on Pd(100)
    • 7.4. Basic Models for CO-oxidation on Other Metal (100) Surfaces
  • 8. Spatiotemporal Behavior in Catalytic Reactions on 2D Metal Surfaces
    • 8.1. General Theory and Analysis for Realistic msLG Models
    • 8.2. Stationary Fronts for the Tailored Model for CO + O on Pd(100)
    • 8.3. Propagating Fronts for the Tailored Model for CO + O on Pd(100)
  • 9. Catalytic Reactions on 2D Metal Oxide Surfaces at High P
    • 9.1. msLG Models for CO-oxidation on RuO2(110)
    • 9.2. Other Reactions on Oxide Surfaces
  • 10. Summary and Prognosis

Supramolecular Catalysis in Metal–Ligand Cluster Hosts

Department of Chemistry, University of California, Berkeley, California 94720-1460, United States
Division of Chemical Sciences, Lawrence Berkeley National Laboratory, Berkeley, California 94720, United States
Chem. Rev., Article ASAP
DOI: 10.1021/cr4001226
Publication Date (Web): April 21, 2015
Copyright © 2015 American Chemical Society
Table of Contents:
  • 1. Introduction
  • 2. Early Examples of Supramolecular Hosts in Chemistry and Catalysis
  • 3. Metallosupramolecular Hosts
    • 3.1. Host Design and Synthesis
    • 3.2. Stoichiometric and Catalytic Chemistry in Supramolecular Coordination Complexes
    • 3.3. Stabilization of Reactive Species within Supramolecular Coordination Cages
  • 4. Transition Metal Chemistry and Catalysts in Supramolecular Hosts
  • 5. Enantioselective Supramolecular Catalysts
  • 6. Conclusions and Outlook

Quantum Mechanical Studies of Large Metal, Metal Oxide, and Metal Chalcogenide Nanoparticles and Clusters

Department of Chemistry, Kansas State University, Manhattan, Kansas 66506, United States
Chem. Rev., Article ASAP
DOI: 10.1021/cr500506r
Publication Date (Web): April 21, 2015
Copyright © 2015 American Chemical Society


Table of Contents:
  • 1. Introduction
    • 1.1. General Background
    • 1.2. Scope
    • 1.3. Theoretical Methods
    • 1.4. General Comments
  • 2. Transition Metal Clusters
    • 2.1. Group 10
      • 2.1.1. Ni Clusters
      • 2.1.2. Pd Clusters
      • 2.1.3. Pt Clusters
    • 2.2. Group 11
      • 2.2.1. Gold
      • 2.2.2. Silver
      • 2.2.3. Copper
      • 2.2.4. Thiolate-Protected Gold Nanoparticles
      • 2.2.5. Halogen-Stabilized Gold Nanoparticles
      • 2.2.6. Phosphine-Passivated Gold Nanoparticles
      • 2.2.7. Iron–Carbonyl Ligands on Gold Nanoparticles
      • 2.2.8. Thiolate-Protected Silver and Copper Nanoparticles
    • 2.3. Group 12
      • 2.3.1. Zn Clusters
      • 2.3.2. Cd Clusters
      • 2.3.3. Hg Clusters
    • 2.4. Other 3d Transition Metal Clusters
      • 2.4.1. Sc Clusters
      • 2.4.2. Ti Clusters
      • 2.4.3. V Clusters
      • 2.4.4. Cr Clusters
      • 2.4.5. Mn Clusters
      • 2.4.6. Fe Clusters
      • 2.4.7. Co Clusters
    • 2.5. Other 4d Transition Metal Clusters
      • 2.5.1. Ru Clusters
      • 2.5.2. Rh Clusters
    • 2.6. Other 5d Transition Metal Clusters
  • 3. Main Group Metal Clusters
    • 3.1. Group 13
      • 3.1.1. Al Clusters
      • 3.1.2. Ga Clusters
    • 3.2. Group 14
      • 3.2.1. Sn Clusters
      • 3.2.2. Pb Clusters
  • 4. Transition Metal Oxides
    • 4.1. Group 3 Oxides
      • 4.1.1. Scandium Oxides
      • 4.1.2. Yttrium Oxides
    • 4.2. Group 4 Oxides
      • 4.2.1. Titanium Oxides
      • 4.2.2. Zirconium Oxides
    • 4.3. Group 5 Oxides
      • 4.3.1. Vanadium Oxides
      • 4.3.2. Niobium Oxides
    • 4.4. Group 6 Oxides
      • 4.4.1. Chromium Oxides
      • 4.4.2. Molybdenum Oxides
      • 4.4.3. Tungsten Oxides
    • 4.5. Group 7 Oxides
      • 4.5.1. Manganese Oxides
    • 4.6. Group 8 Oxides
      • 4.6.1. Iron Oxides
      • 4.6.2. Ruthenium Oxides
    • 4.7. Group 9 Oxides
      • 4.7.1. Cobalt Oxides
      • 4.7.2. Rhodium Oxides
      • 4.7.3. Iridium Oxides
    • 4.8. Group 10 Oxides
      • 4.8.1. Nickel Oxides
      • 4.8.2. Palladium Oxides
      • 4.8.3. Platinum Oxides
    • 4.9. Group 11 Oxides
      • 4.9.1. Copper Oxides
      • 4.9.2. Silver Oxides
    • 4.10. Group 12 Oxides
      • 4.10.1. Zinc Oxides
      • 4.10.2. Cadmium Oxides
      • 4.10.3. Mercuric Oxides
    • 4.11. Polyoxometalates
  • 5. Semiconducting Metal Chalcogenide Clusters
    • 5.1. Group 12: AIIBVI (AII = Cd, Zn, Hg; BVI = S, Se, Te)
      • 5.1.1. Cadmium Chalcogenides: CdS, CdSe, and CdTe
      • 5.1.2. Zinc Chalcogenides: ZnS, ZnSe, and ZnTe
      • 5.1.3. Mercury Chalcogenides: HgS, HgSe, and HgTe
    • 5.2. Group 13: AIIIBVI (AIII = Ga; BVI = S, Te)
      • 5.2.1. Gallium Sulfide
      • 5.2.2. Gallium Telluride
    • 5.3. Group 14: AIVBVI (AIV = Ge, Pb; BVI = S, Se, Te)
      • 5.3.1. Germanium Chalcogenides: GeS and GeSe
      • 5.3.2. Lead Chalcogenides: PbS, PbSe, and PbTe
  • 6. Summary

Stimuli-Responsive Metal–Ligand Assemblies

Department of Chemistry, University of Cambridge, Lensfield Road, Cambridge CB2 1EW, United Kingdom
Chem. Rev., Article ASAP
DOI: 10.1021/cr500632f
Publication Date (Web): April 16, 2015
Copyright © 2015 American Chemical Society

Table of Contents:
  • 1. Introduction
    • 1.1. Scope of the Review
  • 2. Transition Metal Solid State Materials
    • 2.1. Mechanically Responsive Solid State Materials
    • 2.2. Chemically Responsive Solid State Materials
    • 2.3. Multistimuli-Responsive Solid State Materials
  • 3. Macrocycles
    • 3.1. Light Responsive Macrocycles
    • 3.2. Chemically Responsive Macrocycles
  • 4. Helicates
    • 4.1. Light Responsive Helicates
    • 4.2. Electrochemically Responsive Helicates
    • 4.3. Chemically Responsive Helicates
    • 4.4. Mechanically Responsive Helicates
  • 5. Noninterlocked Molecular Machines, Switches, and Mechanisms
    • 5.1. Metal Ion Translocation Systems
      • 5.1.1. Chemically Responsive Systems
      • 5.1.2. pH Responsive Systems
      • 5.1.3. Electrochemically Responsive Systems
      • 5.1.4. Multistimuli-Responsive Systems
    • 5.2. Molecular Tweezers
      • 5.2.1. Chemically Responsive Molecular Tweezers
    • 5.3. Molecular Scissors
    • 5.4. Self-Locking Systems
      • 5.4.1. Chemically Responsive Self-Locking Systems
      • 5.4.2. Light Responsive Self-Locking Systems
    • 5.5. Molecular Rotors
      • 5.5.1. Chemically Responsive Molecular Rotors
      • 5.5.2. Light Responsive Molecular Rotors
      • 5.5.3. Electrochemically Responsive Molecular Rotors
      • 5.5.4. Acid–Base Responsive Molecular Rotors
  • 6. Molecular Machines, Switches, and Mechanisms Based on Interlocked Structures
    • 6.1. Catenane-Based Molecular Locks
      • 6.1.1. Heat Responsive Molecular Locks
      • 6.1.2. Light Responsive Molecular Locks
    • 6.2. Catenane-Based Molecular Pirouettes
      • 6.2.1. Chemically Responsive Molecular Pirouettes
      • 6.2.2. Electrochemically Responsive Molecular Pirouettes
      • 6.2.3. Light Responsive Molecular Pirouettes
    • 6.3. Rotaxane-Based Molecular Pirouettes
      • 6.3.1. Electrochemically Responsive Molecular Pirouettes
      • 6.3.2. Chemically Responsive Molecular Pirouettes
      • 6.3.3. Multistimuli-Responsive Molecular Pirouettes
    • 6.4. Rotaxane-Based Molecular Muscles
      • 6.4.1. Chemically Responsive Molecular Muscles
      • 6.4.2. Acid–Base Responsive Molecular Muscles
      • 6.4.3. Light Responsive Molecular Muscles
      • 6.4.4. Multistimuli-Responsive Molecular Muscles
    • 6.5. Rotaxane-Based Molecular Shuttles
      • 6.5.1. Chemically Responsive Molecular Shuttles
      • 6.5.2. Electrochemically Responsive Molecular Shuttles
      • 6.5.3. Light Responsive Molecular Shuttles
      • 6.5.4. Multistimuli-Responsive Molecular Shuttles
  • 7. Metal–Organic Cages
    • 7.1. Light Responsive Metal–Organic Cages
      • 7.1.1. Light-Driven Structural Reconfiguration
      • 7.1.2. Photoactive Hosts
    • 7.2. Electrochemically Responsive Metal–Organic Cages
    • 7.3. Chemically Responsive Metal–Organic Cages
      • 7.3.1. pH Responsive Metal–Organic Cages
      • 7.3.2. Guest Responsive Metal–Organic Cages
      • 7.3.3. Coordinatively Responsive Metal–Organic Cages
      • 7.3.4. Solvent Responsive Cage Assemblies
  • 8. Polymers and Gels
    • 8.1. Hierarchical Assembly of Discrete Structures
      • 8.1.1. Chemically Responsive Systems
      • 8.1.2. Light Responsive Systems
      • 8.1.3. Multistimuli-Responsive Systems
    • 8.2. Metal Ions as Bridges
      • 8.2.1. Light Responsive Systems
      • 8.2.2. Chemically Responsive Systems
      • 8.2.3. Redox Responsive Systems
      • 8.2.4. Multistimuli-Responsive Polymers
    • 8.3. Miscellaneous
  • 9. Conclusions and Future Outlook