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https://www.readbyqxmd.com/read/28443889/the-passivating-effect-of-cadmium-in-pbs-cds-colloidal-quantum-dots-probed-by-nm-scale-depth-profiling
#1
Pip C J Clark, Hanna Radtke, Atip Pengpad, Andrew I Williamson, Ben F Spencer, Samantha J O Hardman, Marina A Leontiadou, Darren C J Neo, Simon M Fairclough, Andrew A R Watt, Igor Pis, Silvia Nappini, Federica Bondino, Elena Magnano, Karsten Handrup, Karina Schulte, Mathieu G Silly, Fausto Sirotti, Wendy R Flavell
Achieving control of the surface chemistry of colloidal quantum dots (CQDs) is essential to fully exploit their properties in solar cells, but direct measurement of the chemistry and electronic structure in the outermost atomic layers is challenging. Here we probe the surface oxidation and passivation of cation-exchanged PbS/CdS core/shell CQDs with sub nm-scale precision using synchrotron-radiation-excited depth-profiling photoemission. We investigate the surface composition of the topmost 1-2.5 nm of the CQDs as a function of depth, for CQDs of varying CdS shell thickness, and examine how the surface changes after prolonged air exposure...
April 26, 2017: Nanoscale
https://www.readbyqxmd.com/read/28442137/enhanced-surface-ozone-during-the-heat-wave-of-2013-in-yangtze-river-delta-region-china
#2
X Pu, T J Wang, X Huang, D Melas, P Zanis, D K Papanastasiou, A Poupkou
Under the background of global warming, occurrence of heat waves has increased in most part of Europe, Asia and Australia along with enhanced ozone level. In this paper, observational air temperature and surface ozone in the Yangtze River Delta (YRD) region of China during summer of 2013, and the regional chemistry-climate model (RegCM-CHEM4) were applied to explore the relationship between heat wave and elevated ground-level ozone. Observations indicated that YRD experienced severe heat waves with maximum temperature up to 41...
April 22, 2017: Science of the Total Environment
https://www.readbyqxmd.com/read/28431206/phase-transfer-ligand-exchange-of-lead-chalcogenide-quantum-dots-for-direct-deposition-of-thick-highly-conductive-films
#3
Qianglu Lin, Hyeong Jin Yun, Wenyong Liu, Hyung-Jun Song, Nikolay S Makarov, Oleksandr Isaienko, Tom Nakotte, Gen Chen, Hongmei Luo, Victor I Klimov, Jeffrey M Pietryga
The use of semiconductor nanocrystal quantum dots (QDs) in optoelectronic devices typically requires post-synthetic chemical surface treatments to enhance electronic coupling between QDs and allow for efficient charge transport in QD films. Despite their importance to solar cells, and infrared (IR) light-emitting diodes and photodetectors, advances in these chemical treatments for lead chalcogenide (PbE, E = S, Se, Te) QDs have lagged behind those of, for instance, II-VI semiconductor QDs. Here, we introduce a method for fast and effective ligand exchange for PbE QDs in solution, resulting in QDs completely passivated by a wide range of small anionic ligands...
April 21, 2017: Journal of the American Chemical Society
https://www.readbyqxmd.com/read/28418703/radioresistance-of-adenine-to-cosmic-rays
#4
Gabriel S Vignoli Muniz, Christian F Mejía, Rafael Martinez, Basile Auge, Hermann Rothard, Alicja Domaracka, Philippe Boduch
The presence of nucleobases in carbonaceous meteorites on Earth is an indication of the existence of this class of molecules in outer space. However, space is permeated by ionizing radiation, which can have damaging effects on these molecules. Adenine is a purine nucleobase that amalgamates important biomolecules such as DNA, RNA, and ATP. Adenine has a unique importance in biochemistry and therefore life. The aim of this work was to study the effects of cosmic ray analogues on solid adenine and estimate its survival when exposed to corpuscular radiation...
April 2017: Astrobiology
https://www.readbyqxmd.com/read/28415861/atmospheric-aerosols-clouds-chemistry-and-climate
#5
V Faye McNeill
Although too small to be seen with the human eye, atmospheric particulate matter has major impacts on the world around us, from our health to global climate. Understanding the sources, properties, and transformations of these particles in the atmosphere is among the major challenges in air quality and climate research today. Significant progress has been made over the past two decades in understanding atmospheric aerosol chemistry and its connections to climate. Advances in technology for characterizing aerosol chemical composition and physical properties have enabled rapid discovery in this area...
April 17, 2017: Annual Review of Chemical and Biomolecular Engineering
https://www.readbyqxmd.com/read/28414388/infrared-spectroscopy-of-secondary-organic-aerosol-precursors-and-investigation-of-the-hygroscopicity-of-soa-formed-from-the-oh-reaction-with-guaiacol-and-syringol
#6
Waed Ahmad, Cecile Coeur, Alexandre Tomas, Thomas Fagniez, Jean-Blaise Brubach, Arnaud Cuisset
Attenuated total reflection Fourier transform infrared spectroscopy (ATR-FTIR) synchrotron analyses supplemented by density functional theory (DFT) anharmonic calculations have been undertaken to study the fundamental vibrational signatures of guaiacol and syringol, two methoxyphenol compounds found at the highest concentrations in fresh wood smoke and precursors of secondary organic aerosols (SOA) affecting the radiative balance and chemistry of the atmosphere. Nitroderivatives of these two compounds have also been studied experimentally for nitroguaiacol and theoretically for nitrosyringol...
April 10, 2017: Applied Optics
https://www.readbyqxmd.com/read/28405645/a-new-model-of-the-chemistry-of-ionizing-radiation-in-solids-ciris
#7
Christopher N Shingledecker, Romane Le Gal, Eric Herbst
The collisions between high-energy ions and solids can result in significant physical and chemical changes to the material. These effects are potentially important for better understanding the chemistry of interstellar and planetary bodies, which are exposed to cosmic radiation and the solar wind, respectively; however, modeling such collisions on a detailed microscopic basis has thus far been largely unsuccessful. To that end, a new model, entitled CIRIS: the Chemistry of Ionizing Radiation in Solids, was created to calculate the physical and chemical effects of the irradiation of solid materials...
April 13, 2017: Physical Chemistry Chemical Physics: PCCP
https://www.readbyqxmd.com/read/28395111/highly-soluble-p-terphenyl-and-fluorene-derivatives-as-efficient-dopants-in-plastic-scintillators-for-sensitive-nuclear-material-detection
#8
Alan Sellinger, Henok A Yemam, Adam Mahl, Uwe Greife, Jonathan Tinkham, Joshua Koubek
Plastic scintillators are commonly used as first-line detectors for special nuclear materials. Current state-of-the-art plastic scintillators based on poly(vinyltoluene) (PVT) matrices containing high loadings (>15.0 wt%) of 2,5-diphenyloxazole (PPO) offer neutron signal discrimination in gamma radiation background (termed pulse shape discrimination, PSD), however they suffer from poor mechanical properties. In this work, a series of p-terphenyl and fluorene derivatives were synthesized and used as dopants in PVT based plastic scintillators as possible alternatives to PPO to address the mechanical property issue and to study the PSD mechanism...
April 10, 2017: Chemistry: a European Journal
https://www.readbyqxmd.com/read/28375902/ergothioneine-antioxidant-function-from-chemistry-to-cardiovascular-therapeutic-potential
#9
Luigi Servillo, Nunzia DʼOnofrio, Maria Luisa Balestrieri
Ergothioneine (ESH), the betaine of 2-mercapto-L-histidine, is a water-soluble naturally occurring amino acid with antioxidant properties. ESH accumulates in several human and animal tissues up to millimolar concentration through its high affinity transporter, namely the organic cation transporter 1 (OCTN1). ESH, first isolated from the ergot fungus (Claviceps purpurea), is synthesized only by Actinomycetales and non-yeast-like fungi. Plants absorb ESH via symbiotic associations between their roots and soil fungi, whereas mammals acquire it solely from dietary sources...
April 2017: Journal of Cardiovascular Pharmacology
https://www.readbyqxmd.com/read/28375692/the-hydrated-electron
#10
John M Herbert, Marc P Coons
Existence of a hydrated electron as a byproduct of water radiolysis was established more than 50 years ago, yet this species continues to attract significant attention due to its role in radiation chemistry, including DNA damage, and because questions persist regarding its detailed structure. This work provides an overview of what is known in regards to the structure and spectroscopy of the hydrated electron, both in liquid water and in clusters (HO)(-)N, the latter of which provide model systems for how water networks accommodate an excess electron...
March 27, 2017: Annual Review of Physical Chemistry
https://www.readbyqxmd.com/read/28373709/the-signs-of-antarctic-ozone-hole-recovery
#11
Jayanarayanan Kuttippurath, Prijitha J Nair
Absorption of solar radiation by stratospheric ozone affects atmospheric dynamics and chemistry, and sustains life on Earth by preventing harmful radiation from reaching the surface. Significant ozone losses due to increases in the abundances of ozone depleting substances (ODSs) were first observed in Antarctica in the 1980s. Losses deepened in following years but became nearly flat by around 2000, reflecting changes in global ODS emissions. Here we show robust evidence that Antarctic ozone has started to recover in both spring and summer, with a recovery signal identified in springtime ozone profile and total column measurements at 99% confidence for the first time...
April 3, 2017: Scientific Reports
https://www.readbyqxmd.com/read/28366679/o2-%C3%A2-and-h2o2-mediated-disruption-of-fe-metabolism-causes-the-differential-susceptibility-of-nsclc-and-gbm-cancer-cells-to-pharmacological-ascorbate
#12
Joshua D Schoenfeld, Zita A Sibenaller, Kranti A Mapuskar, Brett A Wagner, Kimberly L Cramer-Morales, Muhammad Furqan, Sonia Sandhu, Thomas L Carlisle, Mark C Smith, Taher Abu Hejleh, Daniel J Berg, Jun Zhang, John Keech, Kalpaj R Parekh, Sudershan Bhatia, Varun Monga, Kellie L Bodeker, Logan Ahmann, Sandy Vollstedt, Heather Brown, Erin P Shanahan Kauffman, Mary E Schall, Ray J Hohl, Gerald H Clamon, Jeremy D Greenlee, Matthew A Howard, Michael K Shultz, Brian J Smith, Dennis P Riley, Frederick E Domann, Joseph J Cullen, Garry R Buettner, John M Buatti, Douglas R Spitz, Bryan G Allen
Pharmacological ascorbate has been proposed as a potential anti-cancer agent when combined with radiation and chemotherapy. The anti-cancer effects of ascorbate are hypothesized to involve the autoxidation of ascorbate leading to increased steady-state levels of H2O2; however, the mechanism(s) for cancer cell-selective toxicity remain unknown. The current study shows that alterations in cancer cell mitochondrial oxidative metabolism resulting in increased levels of O2(⋅-) and H2O2 are capable of disrupting intracellular iron metabolism, thereby selectively sensitizing non-small-cell lung cancer (NSCLC) and glioblastoma (GBM) cells to ascorbate through pro-oxidant chemistry involving redox-active labile iron and H2O2...
April 10, 2017: Cancer Cell
https://www.readbyqxmd.com/read/28364699/deciphering-the-influence-of-column-chemistry-and-mass-spectrometry-settings-for-the-analyses-of-geometrical-isomers-of-l-chicoric-acid
#13
Keabetswe Masike, Fidele Tugizimana, Nombuso Ndlovu, Elize Smit, Louis du Preez, Ian Dubery, Edwin Madala
Resolving the chemo-diversity of plant extract samples is an essential step for in-depth analyses of natural products which often exhibit promising biological activities. One of the challenges in this endeavor has been the confident differentiation of geometrical isomers. In this study, we investigated these aspects in chromatography (column chemistry and mobile phase composition) and mass spectrometry settings with regards to better differentiation of geometrical isomers. A standard of a hydroxycinnamic acid (HCA) derivative, L-chicoric acid (L-CA) - a di-acylated caffeoyltartaric acid ester found in a number of plant families - was used...
March 24, 2017: Journal of Chromatography. B, Analytical Technologies in the Biomedical and Life Sciences
https://www.readbyqxmd.com/read/28363019/low-temperature-synchrotron-photoionization-study-of-2-methyl-3-buten-2-ol-mbo-oxidation-initiated-by-o-3-p-atoms-in-the-298-650-k-range
#14
Yasmin Fathi, Chelsea Price, Giovanni Meloni
This work studies the oxidation of 2-methyl-3-buten-2-ol initiated by O((3)P) atoms. The oxidation was investigated at room temperature, 550, and 650 K. Using the synchrotron radiation from the Advanced Light Source (ALS) of the Lawrence Berkley National Laboratory, reaction intermediates and products were studied by multiplexed photoionization mass spectrometry. Mass-to-charge ratios, kinetic time traces, photoionization spectra, and adiabatic ionization energies for each primary reaction species were obtained and used to characterize their identity...
April 20, 2017: Journal of Physical Chemistry. A
https://www.readbyqxmd.com/read/28338703/theoretical-investigation-of-proton-collisions-on-prebiotic-candidates-hydrogen-cyanide-polymers
#15
Marie-Christine Bacchus-Montabonel
One of the major concerns in prebiotic chemistry is the formation and destruction routes of prebiotic compounds in space. As detected for a long time, hydrogen cyanide (HCN) has been suggested to be a feedstock molecule at the origin of life driving easy oligomerization, in particular to form adenine. This may focus on its first oligomers because its dimer cyanomethanimine was recently observed in star-forming regions, or its trimer aminomalononitrile. With regard to the assumption of an extra-terrestrial origin of life, the stability of such species under ultraviolet radiation or in ion-collisions is an open question...
March 24, 2017: Physical Chemistry Chemical Physics: PCCP
https://www.readbyqxmd.com/read/28336860/light-emission-intensities-of-luminescent-y%C3%A2-o%C3%A2-eu-and-gd%C3%A2-o%C3%A2-eu-particles-of-various-sizes
#16
Jens Adam, Wilhelm Metzger, Marcus Koch, Peter Rogin, Toon Coenen, Jennifer S Atchison, Peter König
There is great technological interest in elucidating the effect of particle size on the luminescence efficiency of doped rare earth oxides. This study demonstrates unambiguously that there is a size effect and that it is not dependent on the calcination temperature. The Y₂O₃:Eu and Gd₂O₃:Eu particles used in this study were synthesized using wet chemistry to produce particles ranging in size between 7 nm and 326 nm and a commercially available phosphor. These particles were characterized using three excitation methods: UV light at 250 nm wavelength, electron beam at 10 kV, and X-rays generated at 100 kV...
January 25, 2017: Nanomaterials
https://www.readbyqxmd.com/read/28327297/first-proof-of-bismuth-oxide-nanoparticles-as-efficient-radiosensitisers-on-highly-radioresistant-cancer-cells
#17
Callum Stewart, Konstantin Konstantinov, Sally McKinnon, Susanna Guatelli, Michael Lerch, Anatoly Rosenfeld, Moeava Tehei, Stéphanie Corde
This study provides the first proof of the novel application of bismuth oxide as a radiosensitiser. It was shown that on the highly radioresistant 9L gliosarcoma cell line, bismuth oxide nanoparticles sensitise to both kilovoltage (kVp) or megavoltage (MV) X-rays radiation. 9L cells were exposed to a concentration of 50μg.mL(-1) of nanoparticle before irradiation at 125kVp and 10MV. Sensitisation enhancement ratios of 1.48 and 1.25 for 125kVp and 10MV were obtained in vitro, respectively. The radiation enhancement of the nanoparticles is postulated to be a combination of the high Z nature of the bismuth (Z=83), and the surface chemistry...
November 2016: Physica Medica: PM
https://www.readbyqxmd.com/read/28323482/constraints-on-the-early-terrestrial-surface-uv-environment-relevant-to-prebiotic-chemistry
#18
Sukrit Ranjan, Dimitar D Sasselov
The UV environment is a key boundary condition to abiogenesis. However, considerable uncertainty exists as to planetary conditions and hence surface UV at abiogenesis. Here, we present two-stream multilayer clear-sky calculations of the UV surface radiance on Earth at 3.9 Ga to constrain the UV surface fluence as a function of albedo, solar zenith angle (SZA), and atmospheric composition. Variation in albedo and latitude (through SZA) can affect maximum photoreaction rates by a factor of >10.4; for the same atmosphere, photoreactions can proceed an order of magnitude faster at the equator of a snowball Earth than at the poles of a warmer world...
March 2017: Astrobiology
https://www.readbyqxmd.com/read/28298101/acetonitrile-cluster-solvation-in-a-cryogenic-ethane-methane-propane-liquid-implications-for-titan-lake-chemistry
#19
L René Corrales, Thomas D Yi, Samantha K Trumbo, David Shalloway, Jonathan I Lunine, David A Usher
The atmosphere of Titan, Saturn's largest moon, exhibits interesting UV- and radiation-driven chemistry between nitrogen and methane, resulting in dipolar, nitrile-containing molecules. The assembly and subsequent solvation of such molecules in the alkane lakes and seas found on the moon's surface are of particular interest for investigating the possibility of prebiotic chemistry in Titan's hydrophobic seas. Here we characterize the solvation of acetonitrile, a product of Titan's atmospheric radiation chemistry tentatively detected on Titan's surface [H...
March 14, 2017: Journal of Chemical Physics
https://www.readbyqxmd.com/read/28285158/catalytic-topological-insulator-bi2se3-nanoparticles-for-in-vivo-protection-against-ionizing-radiation
#20
Xiao-Dong Zhang, Yaqi Jing, Shasha Song, Jiang Yang, Jun-Ying Wang, Xuhui Xue, Yuho Min, Gyeongbae Park, Xiu Shen, Yuan-Ming Sun, Unyong Jeong
Bi2Se3 nanoparticles (NPs) have attracted wide interests in biological and medical applications. Layer-like Bi2Se3 with high active surface area is promising for free radical scavenging. Here, we extended the medical applications of Bi2Se3 NPs further to in vivo protection against ionizing radiation based on their superior antioxidant activities and electrocatalytic properties. It was found that Bi2Se3 NPs can significantly increase the surviving fraction of mice after exposure of high-energy radiation of gamma ray...
March 8, 2017: Nanomedicine: Nanotechnology, Biology, and Medicine
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