The interlayer space of 2D materials can be a slit reactor where transformations not typical for the gas phase occur. We report redox reactions involving acetonitrile and nitrogen oxide guests in ...galleries of fluorinated graphite. Fluorinated graphite intercalation compounds with acetonitrile are treated with dinitrogen tetraoxide and the synthesis products are studied by a set of experimental methods. Data analysis reveals that N
2
O
4
dissociates in fluorinated graphite matrices to form nitrogen-containing species NO
3
, NO
2
, NO, and N
2
. The interaction of NO
3
with acetonitrile yields HNO
3
, which predominates as a guest in the synthesis products independently of the fluorination degree of the matrix. This reaction is accompanied by the removal of fluorine atoms weakly bonded to the graphite layers, leading to partial defluorination of the matrices. Our work demonstrates the possibility of using fluorinated graphite as a test nanoreactor whose dimension can be controlled by fluorination of the layers.
The insertion of N
2
O
4
into a fluorinated graphite matrix with acetonitrile initiates redox reactions in the interlayer space.
Hypoxia is a major pathogenetic factor in many cancers. Individual resistance to suboptimal oxygen availability is subject to broad variation and its possible role in tumorigenesis remains ...underexplored. This study aimed at specific characterization of glioblastoma progression in male tolerant and susceptible to hypoxia Wistar rats. Hypoxia resistance was assessed by gasping time measurement in an 11,500 m altitude-equivalent hypobaric decompression chamber. Based on the outcome, the animals were assigned to three groups termed 'tolerant to hypoxia' (n = 13), 'normal', and 'susceptible to hypoxia' (n = 24). The 'normal' group was excluded from subsequent experiments. One month later, the animals underwent inoculation with rat glioblastoma 101.8 followed by monitoring of survival, body weight dynamics and neurological symptoms. The animals were sacrificed on post-inoculation days 11 (subgroup 1) and 15 (subgroup 2). Relative vessels number, necrosis areas and Ki-67 index were assessed microscopically; tumor volumes were determined by 3D reconstruction from histological images; serum levels of HIF-1α, IL-1β, and TNFα were determined by ELISA. None of the tolerant to hypoxia animals died of the disease during observation period, cf. 85% survival on day 11 and 55% survival on day 15 in the susceptible group. On day 11, proliferative activity of the tumors in the tolerant animals was higher compared with the susceptible group. On day 15, proliferative activity, necrosis area and volume of the tumors in the tolerant to hypoxia animals were higher compared with the susceptible group. ELISA revealed no dynamics in TNFα levels, elevated levels of IL-1β in the susceptible animals on day 15 in comparison with day 11 and tolerant ones. Moreover, there were elevated levels of HIF-1α in the tolerant animals on day 15 in comparison with day 11. Thus, the proliferative activity of glioblastoma cells and the content of HIF-1α were higher in tolerant to hypoxia rats, but the mortality associated with the tumor process and IL-1β level in them were lower than in susceptible animals. Specific features of glioblastoma 101.8 progression in tolerant and susceptible to hypoxia rats, including survival, tumor growth rates and IL-1β level, can become the basis of new personalized approaches for cancer diseases treatment in accordance to individual hypoxia resistance.
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•Shear stress is used to produce starch-chitosan films of improved quality.•Chitosans with high and low (LDC) deacetylation degree were used.•Аctivation increases flexibility, ...smoothness and transparency of films.•Mechanoactivation result in rise in films tensile strength of 1.5–2.5 time.•Shear-initiated gelation has been proved in blends with high LDC content.
The effect of composition and mechanoactivation in the rotor-stator device on the rheological and film-forming properties of casting blends based on corn starch and chitosans with high (HDC) and low (LDC) deacetylation degree was studied. Films were characterized using optical and atomic force microscopy, X-ray diffraction, FTIR-spectroscopy and by tensile and moisture permeability testing data. An increase in chitosan content was found to result in the blends viscosity increase as well as the tensile strength, elongation and moisture permeability of films. Mechanoactivation was shown to cause an increase in the homogeneity, smoothness and transparency of the films, and an increase in the tensile strength by 1.5 and 2.5 times for the HDC and LDC based films, respectively. It is concluded that the developed eco-friendly and easily implemented method, which allows improving the unsatisfactory properties of starch-chitosan films without the introduction of additional chemicals, can be used on an industrial scale.
Nitrogen-doped carbon nanomaterials have greater capacity and better cycling stability for Li-ion batteries as compared to undoped carbon materials. In situ near-edge X-ray absorption fine structure ...(NEXAFS) spectroscopy in combination with quantum chemical modeling has been applied to determine the chemical states of the incorporated nitrogen after interaction with lithium. NEXAFS N K-edge spectra of nitrogen-doped porous carbon were measured before and after thermal deposition of Li vapors. The simulation and interpretation of NEXAFS data were carried out based on density functional theory calculations of initial and lithiated graphene fragments that contained different nitrogen species. The preferable interactions of Li with pyridinic and hydrogenated pyridinic nitrogen which are located at edges of atomic vacancies and graphene planes were revealed.
A chemical procedure for modification of double-walled carbon nanotubes (DWCNTs) to enhance their response to humidity was developed. The DWCNTs walls were etched by hot concentrated sulfuric acid, ...after what the edge carbon sites were saturated by chlorine via reaction with CCl4 vapor. This treatment increases the dispersibility of DWCNTs in solvents, removes oxygen groups, and produces chlorine-decorated holes in the outer walls. Networks of chlorinated holey DWCNTs showed a high repeatable response to humid environment and a good reversible behavior after the sensor purging by dry air. The density functional theory calculations predict enhanced polarization of the DWCNTs when they contain chlorine-decorated holes in the outer walls and physisorption of H2O molecules near chlorine atoms. These two effects are the cause of an intense low-noise signal to gaseous H2O and easy sensor recovery.
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We report the MoS2/graphene coupling as the result of the decomposition of a mixture of ammonium tetrathiomolybdate and graphene oxide in thermal shock conditions. X-ray diffraction and Raman ...spectroscopy showed that the temperature of 400 °C is sufficient for the formation of MoS2 crystallites. High-resolution electron microscopy detected that nanoscale MoS2 crystallites are oriented along or perpendicular to the graphene surface or they are incorporated between the graphene layers. Electron energy loss C K-edge spectra confirmed a firm bonding between the components. Used as the electrodes of Li-ion batteries, the materials were able to sustain a specific capacity of 564 mAhg−1 at a current density of 10 Ag–1 with gradual growth of the capacity up to ∼1730 mAhg−1 during next 425 operation cycles at 0.1 Ag–1. Our study revealed that rapid decomposition of the precursors creates defects in the graphene and MoS2 layers, short synthesis time enables the formation of few-layer MoS2 nanosheets, and high pressure, developed in the reactor, leads to covalent bonding between the components. These structural features ensure many sites for the adsorption of Li ions, fast transport of the ions, and high stability of the electrode during long-term operation of the battery.
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Intercalated compound of graphite fluoride with n-heptane has been synthesized at room temperature using a multi-stage process including fluorination by a gaseous BrF3 and a set of intercalant ...exchange reactions. It was found that composition of the compound is CF0.40(C7H16)0.04 and the guest molecules interact with the graphite fluoride layers through the van der Waals forces. Since the distance between the filled layers is 1.04nm and the unfilled layers are separated by ∼0.60nm, the obtained compound can be considered as a stack of the fluorinated graphenes. These fluorinated graphenes are large in area making it possible to study local destruction of the π conjugated system on the basal plane. It was shown that fluorine atoms form short chains, while non-fluorinated sp2 carbon atoms are organized in very narrow ribbons and aromatic areas with a size smaller than 3nm. These π electron nanochains and nanoislands preserved after the fluorination process are likely responsible for the value of the energy gap of the compound of ∼2.5eV. Variation in the size and the shape of π electron regions within the fluorinated graphene layers could be a way for tuning the electronic and optical characteristics of the graphene-based materials.
We present a multiyear time series of column abundances of carbon monoxide (CO), hydrogen cyanide (HCN), and ethane (C2H6) measured using Fourier-transform infrared (FTIR) spectrometers at 10 sites ...affiliated with the Network for the Detection of Atmospheric Composition Change (NDACC). Six are high-latitude sites: Eureka, Ny-Ålesund, Thule, Kiruna, Poker Flat, and St. Petersburg, and four are midlatitude sites: Zugspitze, Jungfraujoch, Toronto, and Rikubetsu. For each site, the interannual trends and seasonal variabilities of the CO time series are accounted for, allowing background column amounts to be determined. Enhancements above the seasonal background were used to identify possible wildfire pollution events. Since the abundance of each trace gas emitted in a wildfire event is specific to the type of vegetation burned and the burning phase, correlations of CO to the long-lived wildfire tracers HCN and C2H6 allow for further confirmation of the detection of wildfire pollution. A GEOS-Chem tagged CO simulation with Global Fire Assimilation System (GFASv1.2) biomass burning emissions was used to determine the source attribution of CO concentrations at each site from 2003 to 2018. For each detected wildfire pollution event, FLEXPART back-trajectory simulations were performed to determine the transport times of the smoke plume. Accounting for the loss of each species during transport, the enhancement ratios of HCN and C2H6 with respect to CO were converted to emission ratios. We report mean emission ratios with respect to CO for HCN and C2H6 of 0.0047 and 0.0092, respectively, with a standard deviation of 0.0014 and 0.0046, respectively, determined from 23 boreal North American wildfire events. Similarly, we report mean emission ratios for HCN and C2H6 of 0.0049 and 0.0100, respectively, with a standard deviation of 0.0025 and 0.0042, respectively, determined from 39 boreal Asian wildfire events. The agreement of our emission ratios with literature values illustrates the capability of ground-based FTIR measurements to quantify biomass burning emissions. We provide a comprehensive dataset that quantifies HCN and C2H6 emission ratios from 62 wildfire pollution events. Our dataset provides novel emission ratio estimates, which are sparsely available in the published literature, particularly for boreal Asian sources.
•A series of LiNbO3:Tb (Tb = 0.1 – 2.89 wt%) crystals was grown.•Crystallization processes of LN:Tb are studied.•Optical and structural properties of LN:Tb are studied.•Optical uniformity and ...photorefractive properties of LN:Tb are studied.•A concentration threshold id detected near Tb ~2.2 – 2.3 wt%.
A series of LiNbO3:Tb crystals was grown (Tb = 0.1 – 2.89 wt%). Processes of crystallization and concentration dependences of optical and structural characteristics were studied in these crystals. Optical uniformity and optical resistance were compared for LiNbO3:Tb crystals of different composition. A concentration threshold was determined for the first time in LiNbO3:Tb crystals near Tb ~2.2 – 2.3 wt%. Anomalies of physic-chemical, optical and structural characteristics are observed in this area. Compositions of optically nonlinear LiNbO3:Tb crystals suitable for laser radiation generation and transformation were chosen.
•Ultrasonication results in replacement of edge CBr bonds by the COH ones.•Adsorption energy of Br2 molecules is higher for pre-sonicated DWCNTs.•Bromine molecules prefer to sit near the edge ...hydroxyl groups.•Hydroxyl-terminated DWCNTs accept electron density from Br2.
Bromination of double-walled carbon nanotubes (DWCNTs) was carried out using a saturated vapor of Br2 at room temperature with or without a pretreatment in bromine water. X-ray photoelectron spectroscopy revealed that ultrasound pretreatment modified the chemical state of bromine in the product. The binding energies of the Br 3d electrons in the pre-sonicated DWCNT sample were between those characteristic of the covalent C–Br bonds and the negatively charged Br2 molecules, observed when the pretreatment was not performed. Raman spectroscopy, however, clearly evidenced Br–Br vibrations in both brominated samples. Calculations of CNT–Br2 models within density functional theory were used to propose that the electronic state of a Br2 molecule depends on the adsorption site. The bromine molecules prefer to be located near edge hydroxyl groups, which acept the electron density from Br2. This increases the binding energy of Br 3d levels as compared to that for Br2 molecules in other adsorption sites.
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