49 research outputs found
Beyond Charge Transfer: The impact of auger recombination and FRET on PL quenching in an rGO-QDs system
PL intensity quenching and the PL lifetime reduction of fluorophores located close to gra‐ phene derivatives are generally explained by charge and energy transfer processes. Analyzing the PL from PbS QDs in rGO/QD systems, we observed a substantial reduction in average PL lifetimes with an increase in rGO content that cannot be interpreted solely by these two processes. To explain the PL lifetime dependence on the rGO/QD component ratio, we propose a model based on the Auger recombination of excitations involving excess holes left in the QDs after the charge transfer process. To validate the model, we conducted additional experiments involving the external engi‐ neering of free charge carriers, which confirmed the role of excess holes as the main QD PL quench‐ ing source. A mathematical simulation of the model demonstrated that the energy transfer between neighboring QDs must also be considered to explain the experimental data carefully. Together, Au‐ ger recombination and energy transfer simulation offers us an excellent fit for the average PL life‐ time dependence on the component ratio of the rGO/QD system
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Dietary Omega-3 Fatty Acids Do Not Change Resistance of Rat Brain or Liver Mitochondria to Ca2+ and/or Prooxidants
Omega-3 polyunsaturated fatty acids (n-3 PUFAs) block apoptotic neuronal cell death and are strongly neuroprotective in acute and chronic neurodegeneration. Theoretical considerations, indirect data, and consideration of parsimony lead to the hypothesis that modulation of mitochondrial pathway(s) underlies at least some of the neuroprotective effects of n-3 PUFAs. We therefore systematically tested this hypothesis on healthy male FBFN1 rats fed for four weeks with isocaloric, 10% fat-containing diets supplemented with 1, 3, or 10% fish oil (FO). High resolution mass spectrometric analysis confirmed expected diet-driven increases in docosahexaenoic acid (DHA, 22:6, n-3) and eicosapentaenoic acid (EPA, 20:5, n-3) in sera, liver and nonsynaptosomal brain mitochondria. We further evaluated the resistance of brain and liver mitochondria to Ca2+ overload and prooxidants. Under these conditions, neither mitochondrial resistance to Ca2+ overload and prooxidants nor mitochondrial physiology is altered by diet, despite the expected incorporation of DHA and EPA in mitochondrial membranes and plasma. Collectively, the data eliminate one of the previously proposed mechanism(s) that n-3 PUFA induced augmentation of mitochondrial resistance to the oxidant/calcium-driven dysfunction. These data furthermore allow us to define a specific series of follow-up experiments to test related hypotheses about the effect of n-3 PUFAs on brain mitochondria
Spectroscopic Evidence for Ca2+ Involvement in the Assembly of the Mn4Ca Cluster in the Photosynthetic Water-Oxidizing Complex
Метилмалоновая ацидурия у детей: клинические рекомендации
Methylmalonic acidemia (aciduria) is an inherited metabolic disturbance from the group of organic acidemias (acidurias). The article presents etiopathogenetic, epidemiological, diagnostic, and therapeutic aspects of the problem. The possibilities of laboratory and instrumental diagnostic methods the tactics of dietary correction of metabolic disorders in acute and interstitial periods of the disease are described in details; features of drug treatment are outlined. The necessary information for clinical practice and patients’ everyday life is given in the article.Метилмалоновая ацидемия (ацидурия) — генетически гетерогенное наследственное заболевание группы органических ацидемий (ацидурий). В статье представлены этиопатогенетические, эпидемиологические, диагностические и терапевтические аспекты данной проблемы. Подробно освещены возможности лабораторных и инструментальных методов диагностики и особенности медикаментозного лечения, изложена тактика диетической коррекции метаболических нарушений в острый и межприступный периоды заболевания. Дана необходимая информация для практических врачей и родителей пациентов
An Unexpected Rearrangement That Disassembles Alkyne Moiety Through Formal Nitrogen Atom Insertion between Two Acetylenic Carbons and Related Cascade Transformations: New Approach to Sampangine
Functionalized rGO Interlayers Improve the Fill Factor and Current Density in PbS QDs-Based Solar Cells
Graphene-quantum dot nanocomposites attract significant attention for novel optoelectronic devices, such as ultrafast photodetectors and third-generation solar cells. Combining the remarkable optical properties of quantum dots (QDs) with the exceptional electrical properties of graphene derivatives opens a vast perspective for further growth in solar cell efficiency. Here, we applied (3-mercaptopropyl) trimethoxysilane functionalized reduced graphene oxide (f-rGO) to improve the QDs-based solar cell active layer. The different strategies of f-rGO embedding are explored. When f-rGO interlayers are inserted between PbS QD layers, the solar cells demonstrate a higher current density and a better fill factor. A combined study of the morphological and electrical parameters of the solar cells shows that the improved efficiency is associated with better layer homogeneity, lower trap-state densities, higher charge carrier concentrations, and the blocking of the minor charge carriers
Microfluidic Vaterite Synthesis: Approaching the Nanoscale Particles
The challenge of continuous CaCO3 particle synthesis is addressed using microfluidic technology. A custom microfluidic chip was used to synthesize CaCO3 nanoparticles in vaterite form. Our focus revolved around exploring one-phase and two-phase synthesis methods tailored for the crystallization of these nanoparticles. The combination of scanning electron microscopy, X-ray diffraction, dynamic light scattering, and small-angle scattering allowed for an evaluation of the synthesis efficiency, including the particle size distribution, morphology, and polymorph composition. The results demonstrated the superior performance of the two-phase system when precipitation occurred inside emulsion microreactors, providing improved size control compared with the one-phase approach. We also discussed insights into particle size changes during the transition from one-phase to two-phase synthesis. The ability to obtain CaCO3 nanoparticles in the desired polymorph form (∼50 nm in size, 86–99% vaterite phase) with the possibility of scaling up the synthesis will open up opportunities for various industrial applications of the developed two-phase microfluidic method
Divergent Cyclizations of 1‑R-Ethynyl-9,10-anthraquinones: Use of Thiourea as a “S<sup>2–</sup>” Equivalent in an “Anchor-Relay” Addition Mediated by Formal C–H Activation
The EtONa-mediated reaction of <i>peri</i>-R-ethynyl-9,10-anthraquinones
with thiourea yields 2-R-7<i>H</i>-dibenzo[<i>de</i>,<i>h</i>]quinolin-7-ones and 2-R-anthra[2,1-<i>b</i>]thiophene-6,11-diones. Although 2-R-7<i>H</i>-dibenzo[<i>de</i>,<i>h</i>]quinolin-7-ones were observed previously
in reactions with other N-centered nucleophiles (hydrazine, guanidine,
and urea), the formation of 2-R-anthra[2,1-<i>b</i>]thiophene-6,11-diones
is a new reactivity path. DFT computations analyzed factors responsible
for the switch in reactivity and the relative importance of two possible
pathways: (1) the “anchor-relay” mechanism mediated
by nucleophilic attack at the carbonyl and (2) direct attack at the
alkyne. The two pathways converge on a vinyl sulfur anion, set up
for a 5-endo-trig cyclization at the <i>ortho</i>-position.
Subsequent rearomatization/oxidation provides the fused thiophene
product via formal C–H activation. The calculations suggest
that the latter pathway, the direct attack at the alkyne, is more
likely, due to the relatively high barrier for the 8-endo-dig cyclization
(pathway 1). Computational insights led to a more selective synthesis
of fused thiophenes, based on the reaction of acetylenic anthraquinones
with sodium sulfide. This reaction does not require prefunctionalization
at the <i>ortho</i>-position since direct C–H activation
is efficient. The absence of fused five-membered heterocycles in earlier
work was investigated computationally. The other N-centered nucleophiles
form stronger anion−π complexes with the electron-deficient
quinone core, promoting carbonyl attack over direct alkyne attack