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05 May 18:52

Transient Absorption Spectroscopy of Anatase and Rutile: The Impact of Morphology and Phase on Photocatalytic Activity

by Xiuli Wang, Andreas Kafizas, Xiaoe Li, Savio J. A. Moniz, Philip J. T. Reardon, Junwang Tang, Ivan P. Parkin and James R. Durrant

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The Journal of Physical Chemistry C
DOI: 10.1021/acs.jpcc.5b01858
18 May 15:36

In Situ Resonant UV-Raman Spectroscopy of Polycyclic Aromatic Hydrocarbons

by Matteo Signorile, Francesca Bonino, Alessandro Damin and Silvia Bordiga

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The Journal of Physical Chemistry C
DOI: 10.1021/acs.jpcc.5b02209
27 Apr 19:21

What Makes a Strong Organic Electron Donor (or Acceptor)?

by Benjamin Eberle, Olaf Hübner, Alexandra Ziesak, Elisabeth Kaifer, Hans-Jörg Himmel

Abstract

Organic electron donors are of importance for a number of applications. However, the factors that are essential for a directed design of compounds with desired reduction power are not clear. Here, we analyze these factors in detail. The intrinsic reduction power, which neglects the environment, has to be separated from extrinsic (e.g., solvent) effects. This power could be quantified by the gas-phase ionization energy. The experimentally obtained redox potentials in solution and the calculated ionization energies in a solvent (modeled with the conductor-like screening model (COSMO)) include both intrinsic and extrinsic factors. An increase in the conjugated π-system of organic electron donors leads to an increase in the intrinsic reduction power, but also decreases the solvent stabilization. Hence, intrinsic and extrinsic effects compete against each other; generally the extrinsic effects dominate. We suggest a simple relationship between the redox potential in solution and the gas-phase ionization energy and the volume of an organic electron donor. We finally arrive at formulas that allow for an estimate of the (gas-phase) ionization energy of an electron donor or the (gas-phase) electron affinity of an electron acceptor from the measured redox potentials in solution. The formulas could be used for neutral organic molecules with no or only small static dipole moment and relatively uniform charge distribution after oxidation/reduction.

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Size matters: A relationship between the gas-phase ionization energy and the experienced redox potential in solution is derived. The results highlight the importance of molecular volume in determining the reduction potential in solution (see figure).

30 Mar 12:54

In-Depth Studies on Rapid Photochemical Activation of Various Sol–Gel Metal Oxide Films for Flexible Transparent Electronics

by Sungjun Park, Kwang-Ho Kim, Jeong-Wan Jo, Sujin Sung, Kyung-Tae Kim, Won-June Lee, Jaekyun Kim, Hyun Jae Kim, Gi-Ra Yi, Yong-Hoon Kim, Myung-Han Yoon, Sung Kyu Park

Despite intensive research on photochemical activation of sol–gel metal oxide materials, the relatively long processing time and lack of deep understanding of the underlying chemical courses have limited their broader impact on diverse materials and applications such as thin-film electronics, photovoltaics, and catalysts. Here, in-depth studies on the rapid photochemical activation of diverse sol–gel oxide films using various spectroscopic and electrical investigations for the underlying physicochemical mechanism are reported. Based on the exhaustive chemical and physical analysis, it is noted that deep ultraviolet-promoted rapid film formation such as densification, polycondensation, and impurity decomposition is possible within 5 min via in situ radical-mediated reactions. Finally, the rapid fabrication of all-solution metal oxide thin-film-transistor circuitry, which exhibits stable and reliable electrical performance with a mobility of >12 cm2 V−1 s−1 and an oscillation frequency of >650 kHz in 7-stage ring oscillator even after bending at a radius of <1 mm is demonstrated.

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The general physicochemical mechanisms underlying photoactivated sol–gel reactions are described, with comprehensive chemical and structural analysis inducing rapid (<5 min) fabrication of various metal oxide films at low temperatures (<150 °C), and all-solution processed high-performance electronic devices and circuitry on ultrathin polymeric substrates are demonstrated. This will open new possibilities to prepare future electronic materials in a fast, scalable, and economic manner.

28 Apr 11:11

Charge Photogeneration in Few-Layer MoS2

by Tetiana Borzda, Christoph Gadermaier, Natasa Vujicic, Peter Topolovsek, Milos Borovsak, Tomaz Mertelj, Daniele Viola, Cristian Manzoni, Eva A. A. Pogna, Daniele Brida, Maria Rosa Antognazza, Francesco Scotognella, Guglielmo Lanzani, Giulio Cerullo, Dragan Mihailovic

The 2D semiconductor MoS2 in its mono- and few-layer form is expected to have a significant exciton binding energy of several 100 meV, suggesting excitons as the primary photoexcited species. Nevertheless, even single layers show a strong photovoltaic effect and work as the active material in high sensitivity photodetectors, thus indicating efficient charge carrier photogeneration. Here, modulation spectroscopy in the sub-ps and ms time scales is used to study the photoexcitation dynamics in few-layer MoS2. The results suggest that the primary photoexcitations are excitons that efficiently dissociate into charges with a characteristic time of 700 fs. Based on these findings, simple suggestions for the design of efficient MoS2 photovoltaic and photodetector devices are made.

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Few-layer MoS2 flakes are intermediates between conventional semiconductors and excitonic nanomaterials. By femtosecond optical pump–probe spectroscopy it is shown that photoexcitation creates excitons as the primary species. The excitons efficiently dissociate into charge carriers with a time constant of 700 fs, making few-layer MoS2 an excellent candidate for efficient photodetectors and photovoltaic devices.

18 May 18:11

Sol–Gel Metal Oxides: In-Depth Studies on Rapid Photochemical Activation of Various Sol–Gel Metal Oxide Films for Flexible Transparent Electronics (Adv. Funct. Mater. 19/2015)

by Sungjun Park, Kwang-Ho Kim, Jeong-Wan Jo, Sujin Sung, Kyung-Tae Kim, Won-June Lee, Jaekyun Kim, Hyun Jae Kim, Gi-Ra Yi, Yong-Hoon Kim, Myung-Han Yoon, Sung Kyu Park
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The front cover demonstrates the fabrication of sol–gel derived metal oxide electronic devices and circuits by low-temperature photochemical activation via in-situ radical-mediated reactions. On page 2807, M.-H. Yoon, S. K. Park, and colleagues show that the rapid photoactivation process enables the conversion of the sol–gel precursors into metal oxide electronic materials directly on ultra-flexible plastic substrates, which will serve as a general methodology in a rapid, scalable, and economic manner.

06 May 12:51

Catalytic Water Oxidation by a Molecular Ruthenium Complex: Unexpected Generation of a Single-Site Water Oxidation Catalyst

by Wangchuk Rabten, Markus D. Kärkäs, Torbjörn Åkermark, Hong Chen, Rong-Zhen Liao, Fredrik Tinnis, Junliang Sun, Per E. M. Siegbahn, Pher G. Andersson and Björn Åkermark

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Inorganic Chemistry
DOI: 10.1021/ic502755c
28 Apr 16:02

An Mn(V)-oxo role in splitting water? [Chemistry]

by Britt, R. D., Suess, D. L. M., Stich, T. A.
The oxygen-evolving complex (OEC) of photosystem II (PSII) uses the full spectrum of visible light to oxidize water, producing O2 and bioactivated electrons and protons (1, 2). The unique nature of this crucial bioenergetic reaction has led to much interest in harnessing analogous photochemistry and catalysis for energy storage, with...
01 May 00:00

Mammoth genomes provide recipe for creating Arctic elephants

by Ewen Callaway

Mammoth genomes provide recipe for creating Arctic elephants

Nature 521, 7550 (2015). http://www.nature.com/doifinder/10.1038/nature.2015.17462

Author: Ewen Callaway

Catalogue of genetic differences between woolly mammoths and elephants reveals how ice-age giants braved the cold.

07 May 18:52

[Report] A synthetic Mn4Ca-cluster mimicking the oxygen-evolving center of photosynthesis

by Chunxi Zhang
Photosynthetic splitting of water into oxygen by plants, algae, and cyanobacteria is catalyzed by the oxygen-evolving center (OEC). Synthetic mimics of the OEC, which is composed of an asymmetric manganese-calcium-oxygen cluster bound to protein groups, may promote insight into the structural and chemical determinants of biological water oxidation and lead to development of superior catalysts for artificial photosynthesis. We synthesized a Mn4Ca-cluster similar to the native OEC in both the metal-oxygen core and the binding protein groups. Like the native OEC, the synthetic cluster can undergo four redox transitions and shows two magnetic resonance signals assignable to redox and structural isomerism. Comparison with previously synthesized Mn3CaO4-cubane clusters suggests that the fourth Mn ion determines redox potentials and magnetic properties of the native OEC. Authors: Chunxi Zhang, Changhui Chen, Hongxing Dong, Jian-Ren Shen, Holger Dau, Jingquan Zhao
07 May 18:52

[This Week in Science] Mimicking the oxygen evolution center

by Nicholas S. Wigginton
Author: Nicholas S. Wigginton
15 May 12:08

Research progress of perovskite materials in photocatalysis- and photovoltaics-related energy conversion and environmental treatment

Chem. Soc. Rev., 2015, Advance Article
DOI: 10.1039/C5CS00113G, Review Article
Wei Wang, Moses O. Tade, Zongping Shao
Perovskite materials are shown to be active in the applications of photocatalysis- and photovoltaics-related energy conversion and environmental treatment.
To cite this article before page numbers are assigned, use the DOI form of citation above.
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05 May 13:37

Formation of Urban Fine Particulate Matter

by Renyi Zhang, Gehui Wang, Song Guo, Misti L. Zamora, Qi Ying, Yun Lin, Weigang Wang, Min Hu and Yuan Wang

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Chemical Reviews
DOI: 10.1021/acs.chemrev.5b00067
12 May 16:50

Can Dynamics Be Responsible for the Complex Multipeak Infrared Spectra of NO Adsorbed to Copper(II) Sites in Zeolites?

by Florian Göltl, Philippe Sautet, Ive Hermans

Abstract

Copper-exchanged SSZ-13 is a very efficient material in the selective catalytic reduction of NOx using ammonia (deNOx-SCR) and characterizing the underlying distribution of copper sites in the material is of prime importance to understand its activity. The IR spectrum of NO adsorbed to divalent copper sites are modeled using ab initio molecular dynamics simulations. For most sites, complex multi-peak spectra induced by the thermal motion of the cation as well as the adsorbate are found. A finite temperature spectrum for a specific catalyst was constructed, which shows excellent agreement with previously reported data. Additionally these findings allow active and inactive species in deNOx-SCR to be identified. To the best of our knowledge, this is the first time such complex spectra for single molecules adsorbed to single active centers have been reported in heterogeneous catalysis, and we expect similar effects to be important in a large number of systems with mobile active centers.

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Theory and practice: The IR spectra of NO adsorbed on Cu centers in a copper-containing zeolite were modeled using molecular dynamics simulations. The spectra are complex, which is due to the thermal motions of the cations and the adsorbates, and are in excellent agreement with the experimental spectra.

25 Mar 00:00

Chemistry: Imaging of excited electron orbitals

Chemistry: Imaging of excited electron orbitals

Nature 519, 7544 (2015). doi:10.1038/519392d

A technique could pave the way for imaging electron behaviour as chemical reactions happen.Many reactions are governed by the behaviour of electrons in excited orbital states, but these states are difficult to capture because they last only a few picoseconds (10−12 seconds).

07 Apr 00:00

The future of the postdoc

by Kendall Powell

The future of the postdoc

Nature 520, 7546 (2015). http://www.nature.com/doifinder/10.1038/520144a

Author: Kendall Powell

There is a growing number of postdocs and few places in academia for them to go. But change could be on the way.

25 Mar 15:20

Facile Synthesis of Crystalline Polymeric Carbon Nitrides with an Enhanced Photocatalytic Performance under Visible Light

by Qinghua Liang, Zheng-Hong Huang, Feiyu Kang, Quan-Hong Yang

Abstract

Poly(triazine imides) intercalated with Li+ and X (PTI/X, X=Cl or Br), which are described widely as crystalline polymeric carbon nitrides, were synthesized in a facile manner by heating a mixture of melamine and LiX. This method has the advantages of low cost, scalable production, and high efficiency. Importantly, both PTI/Cl and PTI/Br exhibit an enhanced photocatalytic performance compared to conventional graphitic polymeric carbon nitride in the degradation of rhodamine B under visible-light irradiation because of their higher visible-light-harvesting ability and charge carrier separation efficiency.

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Easy does it: Crystalline polymeric graphitic carbon nitrides with an enhanced visible-light-driven photocatalytic performance are prepared by heating a mixture of melamine and lithium halides.

16 Apr 12:16

Cover Picture: Synthesis of a Fe–Ni Alloy on a Ceria Support as a Noble-Metal-Free Catalyst for Hydrogen Production from Chemical Hydrogen Storage Materials (ChemCatChem 8/2015)

by Kohsuke Mori, Tomohisa Taga, Hiromi Yamashita
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The cover picture shows effective hydrogen production from an aqueous solution of ammonia-borane (NH3-BH3, AB) by bimetallic FeNi nanoparticles supported on CeO2. In their Full Paper, K. Mori, T. Taga, and H. Yamashita show highly dispersed and partially oxidized amorphous FeNi NPs stabilized by strong interaction with the CeO2 is active for the catalytic dehydrogenation of AB. The advantages of this catalytic system, such as the facile preparation method, free of noble metals, and high recyclability are particularly desirable for a hydrogen vector in terms of potential industrial application in fuel cells. The article highlighted by this cover can be found on p. 1285 ff. of Issue 8, 2015.

17 Apr 20:30

Merging Surface Organometallic Chemistry with Graphitic Carbon Nitride Photocatalysis for CO2 Photofixation

by Guigang Zhang, Zhi-An Lan, Xinchen Wang
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On the surface: The reaction kinetics of CO2 photocatalytic reduction to formic acid on graphitic carbon nitride polymers can be promoted by surface organometallic chemistry. C.B.=Conduction band, V.B.=Valance band, D=electron donor.

26 Mar 10:17

EPR Spectroscopic Detection of the Elusive FeVO Intermediates in Selective Catalytic Oxofunctionalizations of Hydrocarbons Mediated by Biomimetic Ferric Complexes

by Oleg Y. Lyakin, Alexandra M. Zima, Denis G. Samsonenko, Konstantin P. Bryliakov and Evgenii P. Talsi

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ACS Catalysis
DOI: 10.1021/acscatal.5b00169
26 Mar 14:33

Substantial Improvement of Pyridine-Carbene Iridium Water Oxidation Catalysts by a Simple Methyl-to-Octyl Substitution

by Ilaria Corbucci, Ana Petronilho, Helge Müller-Bunz, Luca Rocchigiani, Martin Albrecht and Alceo Macchioni

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ACS Catalysis
DOI: 10.1021/acscatal.5b00319
30 Mar 17:30

Theoretical Studies on the Mechanism of Homogeneous Catalytic Olefin Hydrogenation and Amine–Borane Dehydrogenation by a Versatile Boryl-Ligand-Based Cobalt Catalyst

by Gaurab Ganguly, Tanmay Malakar and Ankan Paul

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ACS Catalysis
DOI: 10.1021/cs501359n
01 Apr 13:06

A Consistent Reaction Scheme for the Selective Catalytic Reduction of Nitrogen Oxides with Ammonia

by Ton V. W. Janssens, Hanne Falsig, Lars F. Lundegaard, Peter N. R. Vennestrøm, Søren B. Rasmussen, Poul Georg Moses, Filippo Giordanino, Elisa Borfecchia, Kirill A. Lomachenko, Carlo Lamberti, Silvia Bordiga, Anita Godiksen, Susanne Mossin and Pablo Beato

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ACS Catalysis
DOI: 10.1021/cs501673g
20 Apr 10:45

Effects of Surface Defects on Photocatalytic H2O2 Production by Mesoporous Graphitic Carbon Nitride under Visible Light Irradiation

by Yasuhiro Shiraishi, Yusuke Kofuji, Hirokatsu Sakamoto, Shunsuke Tanaka, Satoshi Ichikawa and Takayuki Hirai

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ACS Catalysis
DOI: 10.1021/acscatal.5b00408
27 Apr 17:07

Catalytic Hydroboration of Carbonyl Derivatives, Imines, and Carbon Dioxide

by Che Chang Chong and Rei Kinjo

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ACS Catalysis
DOI: 10.1021/acscatal.5b00428
17 Apr 18:28

Noble metal-free hydrogen evolution catalysts for water splitting

Chem. Soc. Rev., 2015, Advance Article
DOI: 10.1039/C4CS00448E, Review Article
Xiaoxin Zou, Yu Zhang
This review summarizes the recent research efforts toward noble metal-free hydrogen evolution electrocatalysts.
To cite this article before page numbers are assigned, use the DOI form of citation above.
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23 Apr 12:32

Steering charge kinetics in photocatalysis: intersection of materials syntheses, characterization techniques and theoretical simulations

Chem. Soc. Rev., 2015, 44,2893-2939
DOI: 10.1039/C5CS00064E, Review Article
Song Bai, Jun Jiang, Qun Zhang, Yujie Xiong
This review outlines the recent progress on probing and steering charge kinetics toward designing highly efficient photocatalysts.
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27 Apr 19:40

Sustainable Chemistry for Energizing the Planet

by Marc Fontecave
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“… There is an unprecedented global consensus that an energetic transition, not to say a revolution, is urgently required. The transition can be defined as the process by which all fossil fuels (and nuclear energy) are replaced by renewable energies. How can we achieve this transition in the shortest time? …” Read more in the Editorial by Marc Fontecave.

09 Mar 00:00

Combined biomass valorization and hydrogen production in a photoelectrochemical cell

by Hyun Gil Cha

Nature Chemistry 7, 328 (2015). doi:10.1038/nchem.2194

Authors: Hyun Gil Cha & Kyoung-Shin Choi

Photoelectrochemical water-splitting produces hydrogen at the cathode and oxygen at the anode. The anode reaction is, however, kinetically unfavourable. Now, reduction of water at the cathode has been combined with oxidation of 5-hydroxymethylfurfural at the anode resulting in a photoelectrochemical cell that produces fuel and a useful platform chemical.

16 Apr 04:24

Stimuli-Responsive Metal–Ligand Assemblies

by Anna J. McConnell, Christopher S. Wood, Prakash P. Neelakandan and Jonathan R. Nitschke

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Chemical Reviews
DOI: 10.1021/cr500632f