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Vincent Deguin, Joëlle Mascetti, Aude Simon, Nadia Ben Amor, Christian Aupetit, Sandra Latournerie, Jennifer Anna Noble
The photochemistry of Fe:H2O adducts is of interest in fields as diverse as catalysis and astrochemistry. Industrially, iron can be used as a catalyst to convert H2O to H2, while in the interstellar medium it may be an important component of dust grains, influencing the chemistry on their icy surfaces. This study consisted of the deposition and spectral characterisation of binary systems of atomic iron with H2O in cryogenic argon matrices. In this way, we were able to obtain information about the interaction of the two species; we observed the formation of adducts of iron monomers and dimers with water molecules in the mid-IR and UV-visible spectral domains...
December 14, 2017: Journal of Physical Chemistry. A
Carlotta Raviola, Maurizio Fagnoni
The site-selective cleavage of an Ar-X bond in polyhalogenated aromatics is an important tool in synthetic planning especially when more than one identical halogen atom is present. An alternative to the usual metal-catalyzed cleavage is represented by photochemistry although only a few examples have been reported. We then investigated the feasibility of the site-selective photodechlorination of some dichloroanisoles through a combined experimental and computational study. In the case of 2,4-dichloroanisole, selective detachment of the chlorine atom at the ortho position with respect to the OMe group was observed upon photohomolysis (in cyclohexane) or photoheterolysis (in MeOH) of the Ar-Cl bond...
December 14, 2017: Photochemical & Photobiological Sciences
Larissa Bergmann, Carolin Braun, Martin Nieger, Stefan Bräse
The prediction of coordination modes is of high importance when structure-property relationships are discussed. Herein, the coordination chemistry of copper(i) with pyridine-amines with a varying number of coordinating N-atoms, namely pyridine-benzimidazole, -triazole and -tetrazole, or their deprotonated analogues, and different phosphines was systematically studied and the photoluminescence properties of all synthesized complexes examined and related to DFT data. Each complex was characterized by single-crystal X-ray analysis and elemental analysis, and a set of prediction rules derived for the coordination chemistry of copper(i) with these ligands...
December 14, 2017: Dalton Transactions: An International Journal of Inorganic Chemistry
Si-Jing Ding, Zhi-Jun Luo, Ya-Ming Xie, Gui-Ming Pan, Yun-Hang Qiu, Kai Chen, Li Zhou, Jianfang Wang, Hai-Qing Lin, Qu-Quan Wang
Colloidal disk-like and sphere-like MoS2 nanoantennas are synthesized. They consist of curly and interlaced 2D nanosheets. The resonance peak of the MoS2 nanoantennas can be tuned from 500 to 900 nm by adjusting the size and shape. The strong magnetic and electric resonances of the dielectric antennas are revealed by theoretical calculations with Mie theory. The second harmonic generation (SHG) of the exfoliated nanosheets and the synthesized nanodisks and nanospheres is investigated and compared by scanning the excitation laser wavelength...
December 12, 2017: Nanoscale
Lauren M Loftus, Ao Li, Kathlyn L Fillman, Philip D Martin, Jeremy J Kodanko, Claudia Turro
Four Ru(II) complexes were prepared bearing two new tetradentate ligands, cyTPA and 1-isocyTPQA, which feature a piperidine ring that provides a structurally rigid backbone and facilitates the installation of other donors as the fourth chelating arm, while avoiding the formation of stereoisomers. The photophysical properties and photochemistry of [Ru(cyTPA)(CH3CN)2]2+ (1), [Ru(1-isocyTPQA)(CH3CN)2]2+ (2), [Ru(cyTPA)(py)2]2+ (3), and [Ru(1-isocyTPQA)(py)2]2+ (4) were compared. The quantum yield for the CH3CN/H2O ligand exchange of 2 was measured to be Φ400 = 0...
December 11, 2017: Journal of the American Chemical Society
Nasim Kashef, Ying-Ying Huang, Michael R Hamblin
The alarming worldwide increase in antibiotic resistance amongst microbial pathogens necessitates a search for new antimicrobial techniques, which will not be affected by, or indeed cause resistance themselves. Light-mediated photoinactivation is one such technique that takes advantage of the whole spectrum of light to destroy a broad spectrum of pathogens. Many of these photoinactivation techniques rely on the participation of a diverse range of nanoparticles and nanostructures that have dimensions very similar to the wavelength of light...
August 2017: Nanophotonics
P Pardha-Saradhi, Nisha Shabnam, P Sharmila, Ashok K Ganguli, Hyunook Kim
Potential impacts of inevitable leaks of silver nanoparticles (AgNPs) into environment on human beings need attention. Owing to the vitality of photosynthesis in maintaining life and ecosystem functioning, impacts of exogenously applied nanoparticulate and Ag+ on photosystem (PS)II function, which governs overall photosynthesis, in wheat and sunflower were evaluated. PSII efficiency and related Chl a fluorescence kinetics of these two plants remained unaffected by AgNPs. However, Ag+ caused a significant decline in the PSII activity and related fluorescence steps in wheat, but not in sunflower...
November 22, 2017: Chemosphere
Magdalena Sałdyka, Zofia Mielke
The products formed during exposure of the CH3CONHOH/Ar (AHA/Ar) matrices to the full output of the Xe lamp and to 225 nm OPO radiation are studied. The irradiation promotes the isomerization, 1Z -1E, and AHA photodissociation reactions. Four pairs of co-products are experimentally found to appear in the photolysis, they form the complexes: CH3OH-HNCO (1), H2O-CH3NCO (2), H2O-CH3CNO (3) and CO-CH3NHOH (4). The structures of the complexes were optimized at the MP2 computational level with the 6-311++G(2d,2p) and aug-cc-pVTZ basis sets...
December 7, 2017: Journal of Physical Chemistry. A
Morgan E Balabanoff, Mahmut Ruzi, David T Anderson
We are studying the details of hydrogen atom (H atom) quantum diffusion in highly enriched parahydrogen (pH2) quantum solids doped with chemical species in an effort to better understand H atom transport and reactivity under these conditions. In this work we present kinetic studies of the 193 nm photo-induced chemistry of methanol (CH3OH) isolated in solid pH2. Short-term irradiation of CH3OH at 1.8 K readily produces CH2O and CO which we detect using FTIR spectroscopy. The in situ photochemistry also produces CH3O and H atoms which we can infer from the post-photolysis reaction kinetics that display significant CH2OH growth...
December 6, 2017: Physical Chemistry Chemical Physics: PCCP
Yang-Er Chen, Hao-Tian Mao, Jie Ma, Nan Wu, Chao-Ming Zhang, Yan-Qiu Su, Zhong-Wei Zhang, Ming Yuan, Huai-Yu Zhang, Xian-Yin Zeng, Shu Yuan
We systematically compared the impacts of four Cr salts (chromic chloride, chromic nitrate, potassium chromate and potassium bichromate) on physiological parameters and chlorophyll fluorescence in indigenous moss Taxiphyllum taxirameum. Among the four Cr salts, K2Cr2O7 treatment resulted in the most significant decrease in photosynthetic efficiency and antioxidant enzymes, increase in reactive oxygen species (ROS), and obvious cell death. Different form the higher plants, although hexavalent Cr(VI) salt treatments resulted in higher accumulation levels of Cr and were more toxic than Cr(III) salts, Cr(III) also induced significant changes in moss physiological parameters and chlorophyll fluorescence...
December 1, 2017: Chemosphere
Hyun-Hang Shin, Gyu Jin Yeon, Han-Kyu Choi, Sang-Min Park, Kang Sup Lee, Zee Hwan Kim
The existence of sub-nm plasmonic hot-spots and their relevance in spectroscopy and microscopy applications remain elusive despite a few recent theoretical and experimental evidences supporting this possibility. In this report, we present new spectroscopic evidence suggesting that angstrom-sized hot-spots exist on the surfaces of plasmon-excited nanostructures. Surface-enhanced Raman scattering (SERS) spectra of 4, 4'-biphenyl dithiols placed in metallic junctions show simultaneously blinking Stokes and anti-Stokes spectra, some of which exhibit only one prominent vibrational peak...
December 5, 2017: Nano Letters
Sergey V Ryazantsev, Jan Lundell, Vladimir I Feldman, Leonid Khriachtchev
We report on the complex of a noble-gas hydride HXeOH with carbon monoxide. This species is prepared via the annealing-induced H + Xe + OH···CO reaction in a xenon matrix, the OH···CO complexes being produced by VUV photolysis of the H2O···CO complexes. The H-Xe stretching mode of the HXeOH···CO complex absorbs at 1590.3 cm-1 and it is blue-shifted by 12.7 cm-1 from the H-Xe stretching band of HXeOH monomer. The observed blue shift indicates the stabilization of the H-Xe bond upon complexation, which is characteristic of complexes of noble-gas hydrides...
December 5, 2017: Journal of Physical Chemistry. A
Xiaohuan Mu, Qinwu Chen, Fanjun Chen, Lixing Yuan, Guohua Mi
Nitrogen is a major limiting factor for crop productivity. The relationship between photosynthesis and nitrogen nutrition has been widely studied. However, the molecular response of leaf photosynthesis to low nitrogen supply in crops is less clear. In this study, RNA sequencing technology (RNA-Seq) was used to investigate the gene expressions related to photosynthesis in maize in response to low nitrogen supply. It was found that low nitrogen supply down-regulated the expression of genes involved in photosystem I (PSI) and photosystem II (PSII)...
December 5, 2017: International Journal of Molecular Sciences
Rui Zhang, Jiasheng Wu, Quan Li, Heikki Hänninen, Chunju Peng, Hang Yao, Xinzhang Song, Yeqing Ying
Atmospheric nitrogen (N) deposition can increase the susceptibility of vascular plants to other stresses, but the physiological basis of such a response remains poorly understood. This study was designed to clarify the physiological mechanisms and to evaluate bioindicators of N deposition impact on vascular plants. We evaluate multiple physiological responses to ~4 years of simulated additional N deposition (30-90 kg N ha-1 year-1) on three age-classes (1a, 3a, and 5a) of Moso bamboo. A saturating response to the additional N deposition was found both in foliar N concentration and in Pn...
2017: Frontiers in Plant Science
Karen Mary Mantovani, Kátia Cristina Molgero Westrup, Renaldo Marcos da Silva Junior, Silvia Jaerger, Fernando Wypych, Shirley Nakagaki
Several functional hybrid materials have been reported as immobilized porphyrin derivatives in various organic and inorganic host materials (polymers, mineral clays, silica, etc.), with potential applications in various fields, such as photochemistry, electrochemistry and heterogeneous catalysis. Layered double hydroxides (LDHs), commonly known as hydrotalcite-like materials, have also been analyzed for use as supports for metallocomplexes. Recently, nanocomposite materials with a core-shell structure produced by combining two kinds of nanometer-size materials have received considerable attention, since the use of these materials is a promising strategy to prevent the aggregation and self-oxidation of molecules, reducing the catalytic activity...
December 4, 2017: Dalton Transactions: An International Journal of Inorganic Chemistry
Jaspreet Walia, Jean-Michel Guay, Oleksiy Krupin, Fabio Variola, Pierre Berini, Arnaud Weck
Plasmon assisted generation of silver sulfate from dodecanethiol is demonstrated on a nano-textured silver substrate with a strong surface plasmon resonance in the visible range. The observed photo-physical processes are attributed to hot charge carriers that are generated from the excitation of surface plasmon resonances using 532 nm laser light. Excited charge carriers are responsible for cleaving the alkane chain, and for generating reactive oxygen species which rapidly photooxidize the exposed sulfur atoms...
December 4, 2017: Physical Chemistry Chemical Physics: PCCP
Alan Deng, Steven G Boxer
Oligohistidine affinity tags (His-tags) are commonly fused to proteins to aid in their purification via metal affinity chromatography. These His-tags are generally assumed to have minimal impact on the properties of the fusion protein, as they have no propensity to form ordered elements, and are small enough not to significantly affect the solubility or size. Here we report structures of two variants of truncated green fluorescent protein (GFP), i.e. split GFP with a β-strand removed, that were found to behave differently in the presence of light...
December 1, 2017: Journal of the American Chemical Society
R D Levine
No abstract text is available yet for this article.
November 30, 2017: Proceedings of the National Academy of Sciences of the United States of America
Yuchao Zhang, Shuai He, Wenxiao Guo, Yue Hu, Jiawei Huang, Justin R Mulcahy, Wei David Wei
Visible-light-driven photochemistry has continued to attract heightened interest due to its capacity to efficiently harvest solar energy and its potential to solve the global energy crisis. Plasmonic nanostructures boast broadly tunable optical properties coupled with catalytically active surfaces that offer a unique opportunity for solar photochemistry. Resonant optical excitation of surface plasmons produces energetic hot electrons that can be collected to facilitate chemical reactions. This review sums up recent theoretical and experimental approaches for understanding the underlying photophysical processes in hot electron generation and discusses various electron-transfer models on both plasmonic metal nanostructures and plasmonic metal/semiconductor heterostructures...
November 30, 2017: Chemical Reviews
Giada Arney, Shawn D Domagal-Goldman, Victoria S Meadows
Early Earth may have hosted a biologically mediated global organic haze during the Archean eon (3.8-2.5 billion years ago). This haze would have significantly impacted multiple aspects of our planet, including its potential for habitability and its spectral appearance. Here, we model worlds with Archean-like levels of carbon dioxide orbiting the ancient Sun and an M4V dwarf (GJ 876) and show that organic haze formation requires methane fluxes consistent with estimated Earth-like biological production rates...
November 30, 2017: Astrobiology
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