Here we report on the spontaneous assembly of Ti
3
C
2
T
x
MXene flakes into monolayer films at the liquid-air interface. According to X-ray reflectivity and grazing incidence X-ray fluorescence both ...the structure of the layers and assembly kinetics depends on the pH value of the solution. At pH > 4 MXene flakes form a single ∼1.5 nm thick layer carrying a negative charge, while in the acidic medium the layer contains coordinated anions with the formation of the Br
aq
−
/Ti
3
C
2
T
x
/subphase interface. The surface layer compression allows the assembling of MXene flakes into a dense monolayer films with the surface coverage of up to 96% and surface pressure exceeding 40 mN m
−1
in the case of the acidic subphase. The films can readily be transferred onto solid substrates by the conventional Langmuir-Blodgett approach or modified by surfactants to form MXene/surfactant composite films.
Here we report on the spontaneous assembly of Ti
3
C
2
T
x
MXene flakes into monolayer films at the liquid-air interface.
Here we report on gas and vapor transport properties of ultra-thin graphene oxide (GO) membranes, with various C:O ratios. Graphene oxide nanosheets with an average lateral size of 800 nm and C:O ...ratio ranging from 2.11 to 1.81 have been obtained using improved Hummers’ method by variation of graphite:KMnO4 ratio. Thin-film selective layers based on the obtained graphene oxide have been spin-coated onto porous substrates. To extend the C:O range to 2.60, thermal reduction of GO membranes was applied. A decrease in C:O ratio leads to significant water vapor permeance growth to over 60 m3(STP)·m−2·bar−1·h−1 while the permeance towards permanent gases reduces slightly. According to the permeation and sorption measurements, a decisive role of H2O diffusivity has been established, while the water sorption capacity of the graphene oxide stays nearly independent of C:O ratio in GO. The result is supported by semi-empirical modeling which reveals diminution of H2O jump activation barriers with both increasing GO interlayer spacing and its oxidation degree. The height of the activation barriers was found to vary up to an order of magnitude within the entire range of relative humidity (0–100% RH), lowering significantly for strongly oxidized GO. Our results evidence the necessity of attaining maximum GO oxidation degree for improving water transport in GO, especially at low partial pressures.
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Bismuth-based compounds are widely used as superconductors, catalysts and materials for optical devices. Their properties, and the possibility of controlling these properties, are determined by their ...electronic structure and the local environment of the Bi-centres. Although X-ray spectroscopy is a powerful method for revealing crystal and electronic structure, the results obtained so far have been limited by the energy resolution of the experimental data. Here, for the first time, we report X-ray absorption near edge structure (XANES) data, recorded in high energy resolution fluorescence detection (HERFD) mode at the Bi LIII and LI edges for a number of bismuth compounds. Experimental data are analysed using ab initio calculations based on a finite difference method (FDMNES) code, for metallic Bi, Bi2O3, BiPO4, Bi4(GeO4)3 and NaBiO3 compounds. It was observed that both the oxidation state and the length of the Bi-ligand bonds determine the exact position of the absorption edge, and this is in good agreement with other studies. Additionally, due to the high energy resolution, spectral features corresponding to strong Bi p-d orbital mixing were resolved. The results obtained here can be used as input for further investigations of the electronic structure of bismuth compounds in different chemical states.
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•High energy resolution x-ray absorption spectroscopy for Bi compounds has been performed.•Experimental results are in good agreement with ab initio calculations.•Resolved pre-edge spectral feature indicates strong p-d orbital mixing.•Mixing with ligand orbitals has been also detected.
We report on the specific properties of O- and OH-terminated Ti3C2Tx nanosheets contributing the permeance of MXene membranes with sorption type selectivity. Thin MXene selective layers on porous ...support demonstrated separation factor for NH3/H2 pair over 50 with ammonia permeance up to 5.0 m3(STP)∙m−2∙bar−1∙h−1 facilitated for humid medium and separation factor for H2O/N2 over 1000 with water permeance over 30 m3(STP)∙m−2∙bar−1∙h−1 close to P0(H2O). According to QCM and GIWAXS studies, high permeance and selectivity of membranes towards ammonia and water vapors are attributed both to ultimate sorption capacity for “basic” vapors and condensation-induced expansion of the interlayer space. Sorption capacity of MXene over 0.045 g∙g(MXene)−1 at 0.3P0 for both NH3 and H2O, significantly exceeds the sorption capacity for permanent gases. Calculations of the diffusion coefficient suggest labyrinthine transport of vapors. For permanent gases no variation of diffusion coefficients was observed with feed pressure, indicating Knudsen diffusion mechanism. Diffusion coefficient of strongly absorbed gases significantly increases with pressure. According to GIWAXS the effect was attributed to the increase of the interlayer distance with saturation of membrane with vapors and reduction of activation barriers for hopping diffusion. Demonstrated characteristics of Ti3C2Tx nanosheets makes it a promising candidate for developing of ammonia selective membranes for Haber-Bosch process membrane extractors.
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•Acidic properties of OH groups on MXene surface determine affinity to “basic” gases.•NH3 sorption coefficient attains 52 mmol/(m3·Pa), drastically exceed sorption for other gases.•Membranes with Ti3C2Tx selective layer were obtained by spin-coating technique.•Selectivity for a NH3/H2 exceeds 50 with ammonia permeance up to 3.91 m3 m−2 bar−1∙h−1.•The increase of interlayer distance with MXene saturation with vapors was founded.
N
-(Prop-2-en-1-yl)hydrazonocarbothioamide reacts with iodoethane in methanol with further addition of 2-hydroxybenzaldehyde to form hydroiodide of carbamohydrazonothioate (HL·HI). The coordination ...compounds were obtained by interaction of HL or HL·HI with copper, nickel, cobalt and iron salts CuLХ·
n
H
2
O X = Cl
–
, Br
–
, NO
3
–
;
n
= 0–1, Ni(L)
2
·HI·CH
3
OH, Сo(L)
2
X X = I
–
, NO
3
–
and Fe(L)
2
NO
3
. The structures of three complexes were established by single crystal X-ray analysis. The synthesized complexes exhibit selective antimicrobial and antifungal activity against a series of standard microorganisms and fungi in the concentration range of 30–500 μg/mL. In addition, nickel and iron complexes selectively inhibit the growth and proliferation of cancer cells and do not adversely affect normal cells.
Thin graphene oxide (GO) membranes supported on porous anodic aluminum oxide (AAO) substrates prepared by spin-coating and pressure-assisted filtration are tested in gas dehumidification experiments. ...Graphene oxides with different specific nanosheet sizes ranged from 10 × 140 to 3300 nm synthesized by modified Hummer's method were used for membrane preparation. We have shown that 25–60 nm-thick GO membranes exhibit barrier properties towards most of the gases (CH4, N2, O2, C4H10), while revealing high permeance for water and water soluble vapors (CO2). The influence of the GO nanosheet size and the membrane preparation technique on the gas transport characteristics of the composite membranes are investigated. The best membrane performance has been achieved for membranes prepared from medium-flake-sized GO nanosheets providing high enough defect density at the surface to allow water entrance to the interlayer space and large enough nanosheet size to cover AAO nanochannels and create continuous barrier coating towards permanent gases on the surface. Water permeance and H2O/N2 selectivity measured in the relative humidity range of 10–80% shows strong humidity dependence due to the sorption of water vapors in the interlayer space of GO. Maximum H2O/N2 selectivity of 13,000 at water permeance of GO membranes of ~1.4 m3/(m2 h) has been achieved at standard conditions (298 K, 1 bar) and relative humidity of 80%. Water permeance of GO membranes strongly depends on the transmembrane pressure, diminishing an order of magnitude from equi-pressure conditions to 0.1 MPa pressure difference. The effect has been ascribed to a pressure-driven ousting of water molecules from the interlayer spacing of GO. Permeability of the GO membranes towards CO2 in humid mixed gas experiments has been shown to be enhanced strongly due to gas solubility in liquefied water enabling sweetening and dehumidification of natural and technological gases in a single stage.
•Membranes with selective graphene oxide layer were obtained by spin-coating technique.•Graphene oxide with different flake size and chemical properties were used for coating.•Membranes shows barrier properties to most of gases and high permeance of water vapor.•Performance of GO membranes is governed by transmembrane pressure and feed humidity.•Permeance of water soluble and non-soluble gases measured for wet and dry gas stream.
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The paper reports pervaporation desalination performance of graphene oxide (GO) membranes for salts solutions. Asymmetrical membranes consisting of GO layer (~5 μm) on polyethersulfone supports ...prepared via pressure-assisted filtration were utilized in the experiments. The initial performance of membranes attaining 27 kg·m−2 h−1 for pure water feed at 80 °C is substantially suppressed with pervaporation from salts solutions down to ~4.5 kg·m−2 h−1 at 0.6 M NaCl concentration. Salts rejection exceeds 99.9 %. According to in-situ and in-operando X-ray scattering study the interlayer distance of GO seriously expands upon ions absorption (up to 5 wt%), varying from 1.45 to 2.67 nm for different cations. The decrease of water permeance, despite of increasing width of the nanochannels, is revealed to originate from increasing activation energy of water molecules transport and diminution of the free volume available for diffusion by >50–80 %. Thus, dynamically changing interlayer distance and loading of graphene oxide with ions are considered the key factors governing the membrane performance. The intercalation of carbon-based spacers (nanoribbons and fullerenols) into interlayer space can be utilized to improve membrane performance. This increases the permeate flux by 70 % compared to pristine GO membranes.
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•The pervaporation desalination performance of graphene oxide membranes was studied.•The membrane performance attaining 27 kg·m−2 h−1 with salts rejection exceeds 99.9 %.•According to X-ray diffraction study varying from 1.45 to 2.67 nm after cation intercalation.•The presence of cations in feed solutions reduce the water permeance by 70–80 %.•The decrease of water permeance explains by reduction volume available for diffusion.
The reaction of
N
-(prop-2-en-1-yl)hydrazinecarbothioamide with substituted 2-hydroxybenzaldehydes afforded the corresponding Schiff bases which were used as ligands to obtain copper and cobalt ...coordination compounds Cu(NL
1–6
)X ·
n
H
2
O (X = Cl
−
,
N
O
3
−
;
n
= 0–3), Co(HL
2
)
2
NO
3
, and Co(NL
6
)
2
Cl. The structure of the isolated complexes was determined by NMR spectroscopy and X-ray analysis. The complexes were tested for antimicrobial and antifungal activity against
S. aureus, E. coli
, and yeast-like fungi. Inhibitory effect of the initial thioamides and their complexes against human myeloid leukemia HL-60 cancer cell line was also studied.
Reaction of pentane-2,4-dione with
N
-(prop-2-en-1-yl)hydrazinecarbothioamide at a 1: 2 molar ratio in ethanol resulted in the formation of a pyrazole derivative. The latter reacted with nickel ...perchlorate at a 1: 1 molar ratio to form the nickel complex with pentane-2,4-dione bis(4-allylthiosemicarbazone). The same type of nickel complex was obtained as a result of
N
-(prop-2-en-1-yl)hydrazinecarbothioamide reaction with pentane-2,4-dione and nickel nitrate at a 2: 1: 1 molar ratio. Antimicrobial, antifungal, antioxidant, and anticancer activities of the obtained compounds were studied.
The crystal structure of the acetic acid solvate of N-(prop-2-en-1-yl)-2-(pyrid-2- ylmethylidene)hydrazinecarboselenoamide (
I
) is determined. The asymmetric unit of the unit cell in its crystal ...structure contains a molecule of
I
and an acetic acid molecule. The molecule of
I
is non-planar; the angle between the mean square planes of hydrazinecarboselenoamide A(Sе1N1N2N3С1C2) and prop-2-en-1-yl (С5С6C7) moieties is 82.3°. In the crystal, the acetic acid molecules link the molecules of
I
in endless chains along the 010 direction.
