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https://www.readbyqxmd.com/read/28549380/synthesis-of-pyridinic-rich-n-s-co-doped-carbon-quantum-dots-as-effective-enzyme-mimics
#1
Teng Liu, Zhi-Wei Cui, Jun Zhou, Ying Wang, Zhi-Gang Zou
N and S co-doped carbon quantum dots (N, S-CQDs) with high N- and S-doping level were synthesized by microwave solid-phase pyrolysis within 50 s. Owing to the dominant pyridinic N injection into the conjugated framework, both high enzyme mimics catalytic activity and photoluminescence quantum yield are achieved simultaneously.
December 2017: Nanoscale Research Letters
https://www.readbyqxmd.com/read/28548683/secondary-rim-%C3%AE-cyclodextrin-functionalization-to-conjugate-with-c60-improved-efficacy-as-photosensitizer
#2
Xiaolei Zhu, Annamaria Quaranta, René Bensasson, Matthieu Sollogoub, Yongmin Zhang
DIBAL-H-mediated demethylation provides a novel entry to secondary rim functionalized γ-CD. 2A,3B-dihydroxyl-per-O-methylated-γ-cyclodextrin has been obtained, whose conjugation with C60 allows the access to the most water-soluble C60 conjugate described so far. The water-solubility 0.12 M (550 mg/mL) is 150 times higher than that of native γ-CD/ C60 complex. Its singlet oxygen (¹O₂) quantum yield is 0.39, an increase by one or two orders of magnitude compared to that of α(β)CD-C60 conjugates.
May 26, 2017: Chemistry: a European Journal
https://www.readbyqxmd.com/read/28548169/photophysicochemical-characterization-of-mycosporine-like-amino-acids-in-micellar-solutions
#3
D E Orallo, S G Bertolotti, M S Churio
The properties and photochemical and photophysical behavior of the mycosporine-like amino acids (MAAs) shinorine and porphyra-334 were experimentally evaluated in solutions of direct ionic micelles as simple biomimicking environments. The preferential partition of the natural molecules in the aqueous phase of sodium dodecyl sulfate (SDS) or cetyltrimethylammonium chloride (CTAC) micellar systems is confirmed. Although the proton dissociation of the carboxylic groups in the MAAs is slightly inhibited in CTAC solutions, the molecules are predicted to be in the form of zwitterions in all the explored media around physiological pH...
May 26, 2017: Photochemical & Photobiological Sciences
https://www.readbyqxmd.com/read/28548097/scalable-focused-ion-beam-creation-of-nearly-lifetime-limited-single-quantum-emitters-in-diamond-nanostructures
#4
Tim Schröder, Matthew E Trusheim, Michael Walsh, Luozhou Li, Jiabao Zheng, Marco Schukraft, Alp Sipahigil, Ruffin E Evans, Denis D Sukachev, Christian T Nguyen, Jose L Pacheco, Ryan M Camacho, Edward S Bielejec, Mikhail D Lukin, Dirk Englund
The controlled creation of defect centre-nanocavity systems is one of the outstanding challenges for efficiently interfacing spin quantum memories with photons for photon-based entanglement operations in a quantum network. Here we demonstrate direct, maskless creation of atom-like single silicon vacancy (SiV) centres in diamond nanostructures via focused ion beam implantation with ∼32 nm lateral precision and <50 nm positioning accuracy relative to a nanocavity. We determine the Si+ ion to SiV centre conversion yield to be ∼2...
May 26, 2017: Nature Communications
https://www.readbyqxmd.com/read/28548092/solid-state-ensemble-of-highly-entangled-photon-sources-at-rubidium-atomic-transitions
#5
Robert Keil, Michael Zopf, Yan Chen, Bianca Höfer, Jiaxiang Zhang, Fei Ding, Oliver G Schmidt
Semiconductor InAs/GaAs quantum dots grown by the Stranski-Krastanov method are among the leading candidates for the deterministic generation of polarization-entangled photon pairs. Despite remarkable progress in the past 20 years, many challenges still remain for this material, such as the extremely low yield, the low degree of entanglement and the large wavelength distribution. Here, we show that with an emerging family of GaAs/AlGaAs quantum dots grown by droplet etching and nanohole infilling, it is possible to obtain a large ensemble of polarization-entangled photon emitters on a wafer without any post-growth tuning...
May 26, 2017: Nature Communications
https://www.readbyqxmd.com/read/28546833/energy-down-converting-organic-fluorophore-functionalized-mesoporous-silica-hybrids-for-monolith-coated-light-emitting-diodes
#6
Markus Börgardts, Thomas J J Müller
The covalent attachment of organic fluorophores in mesoporous silica matrices for usage as energy down converting phosphors without employing inorganic transition or rare earth metals is reported in this article. Triethoxysilylpropyl-substituted derivatives of the blue emitting perylene, green emitting benzofurazane, and red emitting Nile red were synthesized and applied in the synthesis of mesoporous hybrid materials by postsynthetic grafting to commercially available MCM-41. These individually dye-functionalized hybrid materials are mixed in variable ratios to furnish a powder capable of emitting white light with CIE chromaticity coordinates of x = 0...
2017: Beilstein Journal of Organic Chemistry
https://www.readbyqxmd.com/read/28544211/highly-luminescent-and-ultra-stable-cspbbr3-pervoskite-quantum-dots-silica-alumina-monolith
#7
Zhichun Li, Long Kong, Shouqiang Huang, Liang Li
We successfully prepared QDs-silica/alumina monolith (QDs-SAM) by a simple sol-gel reaction of Al-Si single precursors with CsPbBr3 QDs blended in toluene solution, without adding water and catalyst. The resultant transparent monolith exhibits high photoluminescence quantum yields (PLQY) up to 90%, and good photostability under strong illumination of blue light for 300 h. We demonstrated that the preliminary ligand exchange of didodecyl dimethyl ammonium bromide (DDAB) was very important to protect CsPbBr3 QDs from the surface damages during sol-gel reaction, which not only allowed us to maintain the original optical properties of CsPbBr3 QDs but also avoided the aggregation of QDs and make the monolith transparent...
May 24, 2017: Angewandte Chemie
https://www.readbyqxmd.com/read/28543913/from-ligand-to-phosphor-rapid-machine-assisted-syntheses-of-substituted-iridium-iii-pyrazolate-complexes-with-tuneable-luminescence
#8
Simon J Pope, Lara Groves, Christiane Schotten, Joseph Beames, James Platts, Duncan Browne, Simon Coles, Peter Horton
A first generation machine-assisted approach towards the preparation of hybrid ligand/metal materials has been explored. A comparison of synthetic approaches demonstrates that incorporation of both flow chemistry and microwave heating, can be successfully applied to the rapid synthesis of a range of new phenyl-1H-pyrazoles (ppz) substituted with electron withdrawing groups (-F, -CF3, -OCF3, -SF5), and these, in turn, can be translated in to heteroleptic complexes, [Ir(ppz)2(bipy)]BF4 (bipy = 2,2'-bipyridine)...
May 22, 2017: Chemistry: a European Journal
https://www.readbyqxmd.com/read/28543812/acetylacetonatebodipy-biscyclometalated-iridium-iii-complexes-effective-strategy-towards-smarter-fluorescent-photosensitizer-agents
#9
Maria J Ortiz, Eduardo Palao, Rebeca Sola-Llano, Andrea Tabero, Hegoi Manzano, Antonia R Agarrabeitia, Angeles Villanueva, Iñigo López-Arbeloa, Virginia Martinez-Martinez
Biscyclometalated Ir(III) complexes involving BODIPY-based ancillary ligands, where the BODIPY unit is grafted to different chelating cores (acetylacetonate for Ir-1 and Ir-2, and bipyridine for Ir-3) by the BODIPY meso position, have been synthesized and characterized. Complexes having the BODIPY moiety directly grafted to acetylacetonate (Ir-1 and Ir-2) exhibit higher absorption coefficient (ca. ε = 4.46 104 M-1 cm-1 and 3.38 104 M-1cm-1 at 517 nm and 594 nm, respectively), higher moderate-fluorescence emission (ca...
May 19, 2017: Chemistry: a European Journal
https://www.readbyqxmd.com/read/28543444/mechanistic-studies-on-the-peroxyoxalate-chemiluminescence-using-sodium-salicylate-as-base-catalyst
#10
Glalci A Souza, André P Lang, Wilhelm J Baader
Mechanistic studies on the peroxyoxalate chemiluminescence are often conducted with imidazole as base and nucleophilic catalyst. However, it is also known that this compound, at high concentrations, leads to a drastic reduction of the chemiluminescence quantum yields, apparently due the destruction of the high-energy intermediate. Consequently, the search for new catalysts for this transformation is of importance for mechanistic studies as well as analytical application. Therefore, we report here a study on the mechanism of the peroxyoxalate reaction with sodium salicylate as base catalyst; which has already been utilized in this reaction, however, no detailed mechanistic investigation is known...
May 23, 2017: Photochemistry and Photobiology
https://www.readbyqxmd.com/read/28542206/carbonyl-based-blue-autofluorescence-of-proteins-and-amino-acids
#11
Chamani Niyangoda, Tatiana Miti, Leonid Breydo, Vladimir Uversky, Martin Muschol
Intrinsic protein fluorescence is inextricably linked to the near-UV autofluorescence of aromatic amino acids. Here we show that a novel deep-blue autofluorescence (dbAF), previously thought to emerge as a result of protein aggregation, is present at the level of monomeric proteins and even poly- and single amino acids. Just as its aggregation-related counterpart, this autofluorescence does not depend on aromatic residues, can be excited at the long wavelength edge of the UV and emits in the deep blue. Differences in dbAF excitation and emission peaks and intensities from proteins and single amino acids upon changes in solution conditions suggest dbAF's sensitivity to both the chemical identity and solution environment of amino acids...
2017: PloS One
https://www.readbyqxmd.com/read/28540380/online-measurement-of-photoisomerisation-efficiency-in-solution-using-ion-mobility-mass-spectrometry
#12
James N Bull, Eduardo Carrascosa, Michael S Scholz, Neville J A Coughlan, Evan J Bieske
The photoisomerisation of charged molecules in solution is probed directly using ion mobility mass spectrometry with electrospray ionisation. The technique is demonstrated using a prototype azoheteroarene cation in methanol. By scanning the wavelength of the excitation light while monitoring the photoisomer intensity a photoisomerisation action spectrum is generated, which, when compared with a conventional absorption spectrum, allows the relative photoisomerisation quantum yield to be determined across a range of wavelengths...
May 25, 2017: Analyst
https://www.readbyqxmd.com/read/28539582/fluorescent-rna-cytosine-analogue-an-internal-probe-for-detailed-structure-and-dynamics-investigations
#13
Anders Foller Füchtbauer, Søren Preus, Karl Börjesson, Scott A McPhee, David M J Lilley, L Marcus Wilhelmsson
The bright fluorescent cytosine analogue tC(O) stands out among fluorescent bases due to its virtually unquenched fluorescence emission in duplex DNA. However, like most reported base analogues, it has not been thoroughly characterized in RNA. We here report on the first synthesis and RNA-incorporation of tC(O), and characterize its base-mimicking and fluorescence properties in RNA. As in DNA, we find a high quantum yield inside RNA duplexes (<ΦF> = 0.22) that is virtually unaffected by the neighbouring bases (ΦF = 0...
May 24, 2017: Scientific Reports
https://www.readbyqxmd.com/read/28538196/self-assembly-of-gd-3-sds-hepes-complex-and-curcumin-entrapment-for-enhanced-stability-fluorescence-image-in-cellular-system
#14
Chonticha Sahub, Gamolwan Tumcharern, Prae Chirawatkul, Vithaya Ruangpornvisuti, Sanong Ekgasit, Supasorn Wanichweacharungruang, Thawatchai Tuntulani, Tanapat Palaga, Boosayarat Tomapatanaget
At present, strategies to disperse hydrophobic molecules in water without altering their chemical structures include conventional surfactant-based micellar and vesicular systems, encapsulation into water dispersible polymeric nanoparticles, and loading onto the surface of various metal nanoparticles. Here, we report a simple and low cost platform to incorporate hydrophobic molecules into a stable water dispersible nanostructure that can significantly increase the stability of the encapsulated materials. The platform is based on the incorporation of hydrophobic molecules into the self-assembled complex of gadolinium ion (Gd(3+)), sodium dodecyl sulfate (SDS), and 4-(2-hydroxyethyl)-1-piperazineethanesulfonic acid (HEPES) called GdSH...
May 13, 2017: Colloids and Surfaces. B, Biointerfaces
https://www.readbyqxmd.com/read/28537771/atmospheric-constraints-on-the-surface-uv-environment-of-mars-at-3-9%C3%A2-ga-relevant-to-prebiotic-chemistry
#15
Sukrit Ranjan, Robin Wordsworth, Dimitar D Sasselov
Recent findings suggest that Mars may have been a clement environment for the emergence of life and may even have compared favorably to Earth in this regard. These findings have revived interest in the hypothesis that prebiotically important molecules or even nascent life may have formed on Mars and been transferred to Earth. UV light plays a key role in prebiotic chemistry. Characterizing the early martian surface UV environment is key to understanding how Mars compares to Earth as a venue for prebiotic chemistry...
May 24, 2017: Astrobiology
https://www.readbyqxmd.com/read/28537395/effects-of-alkyl-groups-on-excess-electron-binding-to-small-sized-secondary-amide-clusters-a-combined-experimental-and-computational-study
#16
Toshihiko Maeyama, Takuto Shimamori, Asuka Fujii
Excess-electron binding to dimers and trimers of secondary amide molecules was studied by a combination of photoelectron spectroscopy and theoretical calculations. Vertical detachment energies (VDEs) of the cluster anions were measured in the range of a few hundred meV. We found a tendency for VDE to decline with extension of alkyl side-chains. It was fairly reproduced by results of quantum chemical calculations based on density functional theory. For the optimized structures of the cluster anions, the excess electron is located diffusively around the dangling NH group of the hydrogen-bond acceptor molecule...
May 24, 2017: Journal of Physical Chemistry. A
https://www.readbyqxmd.com/read/28537370/red-emissive-carbon-dots-for-fingerprints-detection-by-spray-method-coffee-ring-effect-and-unquenched-fluorescence-in-drying-process
#17
Jie Chen, Ji-Shi Wei, Peng Zhang, Xiao-Qing Niu, Wei Zhao, Ze-Yang Zhu, Hui Ding, Huan-Ming Xiong
Brightly red fluorescent carbon dots are synthesized hydrothermally and dissolved in diluted hydrochloric acid solution. Such carbon dots exhibit excitation-independent emission at about 620 nm with quantum yield over 10%, which is visible in daylight. After the carbon dots solution is sprayed to the fingerprints on various solid substrates and dried in air, clear fingerprints can be seen under an ultraviolet lamp and stay stable for 1 day. Detailed characterizations suggest that during the drying process, the coffee-ring effect and the electrostatic interactions between the carbon dots and the fingerprint residues prevent the typical aggregation-induced fluorescence quenching of carbon dots...
May 24, 2017: ACS Applied Materials & Interfaces
https://www.readbyqxmd.com/read/28537281/comprehensive-theoretical-study-of-all-1812-c60-isomers
#18
Rebecca Sure, Andreas Hansen, Peter Schwerdtfeger, Stefan Grimme
We investigate all 1812 isomers of the fullerene C60 consistently with high-accuracy quantum chemistry methods. The isomers are optimized at the PBE-D3/def2-TZVP level of theory and their relative energies are obtained at the affordable and accurate hybrid-DFT level PW6B95-D3(ATM)/def2-QZVP. For the first time reliable values for the relative energy distribution among the 1812 isomers (maximum value of 549.1 kcal mol(-1), average value of 189.8 ± 46.8 kcal mol(-1), 1267 isomers in an energy window of 150-250 kcal mol(-1)) are given...
May 24, 2017: Physical Chemistry Chemical Physics: PCCP
https://www.readbyqxmd.com/read/28537017/copper-bioaccumulation-photosystem-ii-functioning-and-oxidative-stress-in-the-seagrass-cymodocea-nodosa-exposed-to-copper-oxide-nanoparticles
#19
Michael Moustakas, Paraskevi Malea, Katerina Haritonidou, Ilektra Sperdouli
Photosynthetic activity, oxidative stress, and Cu bioaccumulation in the seagrass Cymodocea nodosa were assessed 4, 12, 24, 48, and 72 h after exposure to two copper oxide nanoparticle (CuO NP) concentrations (5 and 10 mg L(-1)). CuO NPs were characterized by scanning electron microscopy (SEM) and dynamic light scattering measurements (DLS). Chlorophyll fluorescence analysis was applied to detect photosystem II (PSII) functionality, while the Cu accumulation kinetics into the leaf blades was fitted to the Michaelis-Menten equation...
May 23, 2017: Environmental Science and Pollution Research International
https://www.readbyqxmd.com/read/28536785/significance-of-accumulation-of-the-alarmone-p-ppgpp-in-chloroplasts-for-controlling-photosynthesis-and-metabolite-balance-during-nitrogen-starvation-in-arabidopsis
#20
Rina Honoki, Sumire Ono, Akira Oikawa, Kazuki Saito, Shinji Masuda
The regulatory nucleotides, guanosine 5'-triphosphate 3'-diphosphate (pppGpp) and guanosine 5'-diphosphate 3'-diphosphate (ppGpp), were originally identified in Escherichia coli, and control a large set of gene expression and enzyme activities. The (p)ppGpp-dependent control of cell activities is referred to as the stringent response. A growing number of (p)ppGpp synthase/hydrolase homologs have been identified in plants, which are localized in plastids in Arabidopsis thaliana. We recently reported that the Arabidopsis mutant overproducing ppGpp in plastids showed dwarf chloroplasts, and transcript levels in the mutant plastids were significantly suppressed...
May 23, 2017: Photosynthesis Research
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