Уважаемые коллеги!Благодарим Вас за проявленный интерес к Четвертой российской конференции «Графен: молекула и 2D кристалл» и желание принять участие в её работе.Конференция проходит в научно-образовательном центре города Новосибирска -Академгородке.Мероприятие посвящено актуальным направлениям исследований и разработок в области углеродных и низкоразмерных материалов.Проведение конференции поможет координации усилий ученых в решении современных проблем материаловедения и привлечению молодых исследователей для решения актуальных научных задач.Оргкомитет выражает особую благодарность НГУ, Центру компетенций НТИ «Моделирование и разработка новых функциональных материалов с заданными свойствами», компаниям «Диаэм», «НТ-МДТ Спектрум Инструментс» и корпорации "Графеновая Долина" за финансовую поддержку и журналам Аналитика, Наноиндустрия и РЭНСИТ за информационную поддержку.Искренне надеемся, что пребывание в Новосибирском Академгородке и в стенах Новосибирского государственного университета оставит множество положительных эмоций и

Partially fluorinated graphites synthesized at room temperature are capable of reversibly accommodating various molecules in the interlayer space. The structures and properties of these intercalation compounds depend on the fluorine content in the matrix and the nature of the guest. In this work, we compare the thermal stability and optical characteristics of (C2Fx)(n) with x = 0.92 and 0.87, intercalated with acetonitrile and 2-butanone. Density functional theory calculations accompany experimental studies. It is shown that guest molecules prefer to be located over the sp(2)-carbon regions remaining in the partially fluorinated graphene layers. The 2-butanone molecule has stronger interactions with the layers due to its larger length, flexibility, and the presence of carbonyl oxygen. As a result, this guest leaves (C2Fx)(n) matrixes at higher temperatures than acetonitrile. Different guest-host interactions cause a change in the electron excitations and photoluminescence of the fluorinated graphite intercalation compounds. In particular, the spectra are red-shifted when the matrices contain 2-butanone. This property can be used to create optical chemisensors based on partially fluorinated graphene layers.

Уважаемые коллеги!Благодарим Вас за проявленный интерес к Четвертой российской конференции «Графен: молекула и 2D кристалл» и желание принять участие в её работе.Конференция проходит в научно-образовательном центре города Новосибирска -Академгородке.Мероприятие посвящено актуальным направлениям исследований и разработок в области углеродных и низкоразмерных материалов.Проведение конференции поможет координации усилий ученых в решении современных проблем материаловедения и привлечению молодых исследователей для решения актуальных научных задач.Оргкомитет выражает особую благодарность НГУ, Центру компетенций НТИ «Моделирование и разработка новых функциональных материалов с заданными свойствами», компаниям «Диаэм», «НТ-МДТ Спектрум Инструментс» и корпорации "Графеновая Долина" за финансовую поддержку и журналам Аналитика, Наноиндустрия и РЭНСИТ за информационную поддержку.Искренне надеемся, что пребывание в Новосибирском Академгородке и в стенах Новосибирского государственного университета оставит множество положительных эмоций и

Layered fluorinated graphite material can become an efficient nanoreactor for photochemical reactions. In this work, we compared the photochemical behavior of partially fluorinated graphite (FG) and FG containing nitrogen oxides in the interlayer space (NOx@FG) under the action of a high-intense polychromatic photon beam from the synchrotron radiation source BESSY II. Analysis of the chemical and electronic states of the samples was performed using X-ray photoelectron spectroscopy and near-edge X-ray absorption fine structure spectroscopy. Density functional theory calculations were used to interpret and analyze the experimental data. It was found that nitrogen oxides promote the photo-induced degradation of the FG matrix, namely, its partial defluorination, formation of vacancies and doping with nitrogen, while the empty FG had a high photoresistance to synchrotron radiation. The results obtained can be used in the development of new approaches to the modification of graphene layers and in the creation of photostable materials for optical elements.

Here, we study the dielectric properties of fluorinated graphites C2Fx with different fluorine contents (x approximate to 1.05, 0.85, and 0.60) and embedded bromine molecules by impedance spectroscopy. An analysis of the results using the Maxwell-Garnett approximation made it possible to estimate the contributions of the fluorinated graphite matrix and bromine guests to the dielectric permittivity of the compound. The permittivity of the C2Fx matrix increases with decreasing fluorine content and does not depend on temperature. The change in the permittivity upon cooling/heating of the samples is provided by the polarization of bromine molecules Br2. The significant temperature-dependent dielectric response of C2F0.60 is associated with the formation of bromine and polybromide ions, such as Br2- and Br3-, in the interlayer space of the matrix. The decrease in the permittivity at low temperature is explained by the freezing of the ion mobility.

Уважаемые коллеги!Благодарим Вас за проявленный интерес к Четвертой российской конференции «Графен: молекула и 2D кристалл» и желание принять участие в её работе.Конференция проходит в научно-образовательном центре города Новосибирска -Академгородке.Мероприятие посвящено актуальным направлениям исследований и разработок в области углеродных и низкоразмерных материалов.Проведение конференции поможет координации усилий ученых в решении современных проблем материаловедения и привлечению молодых исследователей для решения актуальных научных задач.Оргкомитет выражает особую благодарность НГУ, Центру компетенций НТИ «Моделирование и разработка новых функциональных материалов с заданными свойствами», компаниям «Диаэм», «НТ-МДТ Спектрум Инструментс» и корпорации "Графеновая Долина" за финансовую поддержку и журналам Аналитика, Наноиндустрия и РЭНСИТ за информационную поддержку.Искренне надеемся, что пребывание в Новосибирском Академгородке и в стенах Новосибирского государственного университета оставит множество положительных эмоций и

Fluorinated graphene-like materials are currently attracting much attention due to the tuning of their properties by changing the fluorine content and pattern on the graphene lattice. In this work, we report the redshift of absorption bands and the suppression (increase) of green (yellow-orange) photoluminescence (PL) in the spectra of transparent CFx crystallites as x decreases from ∼0.44 to ∼0.33. Time-dependent density functional theory (TDDFT) calculations reveal that the aromatic regions and polyene chains in the CFx layers are mainly responsible for the optical absorption of the samples in the ultraviolet and visible regions, respectively. The electron-hole recombination within branched aromatic rings or long carbon chains produces orange-red emission, while green-yellow PL is due to transitions of excited polyene electrons to half-occupied levels of aromatic carbon. Our results show that the optical properties of partially fluorinated graphite layers are determined by the size and shape of the remaining sp2 carbon regions, which can be varied by changing the fluorination conditions.

Fluorinated graphitic layers with good mechanical and chemical stability, polar C–F bonds, and tunable bandgap are attractive for a variety of applications. In this work, we investigated the photolysis of fluorinated graphites with interlayer embedded acetonitrile, which is the simplest representative of the acetonitrile-containing photosensitizing family. The samples were continuously illuminated in situ with high-brightness non-monochromatized synchrotron radiation. Changes in the compositions of the samples were monitored using X-ray photoelectron spectroscopy and near-edge X-ray absorption fine structure (NEXAFS) spectroscopy. The NEXAFS N K-edge spectra showed that acetonitrile dissociates to form HCN and N2 molecules after exposure to the white beam for 2 s, and the latter molecules completely disappear after exposure for 200 s. The original composition of fluorinated matrices CF0.3 and CF0.5 is changed to CF0.10 and GF0.17, respectively. The highly fluorinated layers lose fluorine atoms together with carbon neighbors, creating atomic vacancies. The edges of vacancies are terminated with the nitrogen atoms and form pyridinic and pyrrolic units. Our in situ studies show that the photolysis products of acetonitrile depend on the photon irradiation duration and composition of the initial CFx matrix. The obtained results evaluate the radiation damage of the acetonitrile-intercalated fluorinated graphites and the opportunities to synthesize nitrogen-doped graphene materials.

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 N2O4 dissociates in fluorinated graphite matrices to form nitrogen-containing species NO3, NO2, NO, and N2. The interaction of NO3 with acetonitrile yields HNO3, 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 electrical conductivity of graphene materials is strongly sensitive to the surface adsorbates, which makes them an excellent platform for the development of gas sensor devices. Functionalization of the surface of graphene opens up the possibility of adjusting the sensor to a target molecule. Here, we investigated the sensor properties of fluorinated graphene films towards exposure to low concentrations of nitrogen dioxide NO2. The films were produced by liquid-phase exfoliation of fluorinated graphite samples with a composition of CF0.08, CF0.23, and CF0.33. Fluorination of graphite using a BrF3/Br2 mixture at room temperature resulted in the covalent attachment of fluorine to basal carbon atoms, which was confirmed by X-ray photoelectron and Raman spectroscopies. Depending on the fluorination degree, the graphite powders had a different dispersion ability in toluene, which affected an average lateral size and thickness of the flakes. The films obtained from fluorinated graphite CF0.33 showed the highest relative response ca. 43% towards 100 ppm NO2 and the best recovery ca. 37% at room temperature.

The interaction of graphite with a gaseous mixture of BrF3 and Br-2 at room temperature produced fluorinated graphite intercalation compounds with bromine. By changing the concentration of BrF3 in Br-2 from 6.2 to 2.9 % we were able to obtain matrices of fluorinated graphene layers (C2Fx)(n) with x= 0.76, 0.66, 0.35, 0.25. It was shown that bromine was completely replaced by acetonitrile in the (C2Fx)(n) with x > 0.6, while two types of guests (CH3CN and Br-2) were present between the layers with the lower fluorine loading. The Van der Waals forces hold CH3CN molecules in the (C2Fx) n host. The interaction of Br-2 molecules with sp(2)-carbon regions remained in the C2Fx layers has donor-acceptor type. The models of guest molecules packing in host matrices (C2Fx) n are considered using the data on the stoichiometry and X-ray diffraction analysis.

Despite decades of study the precise behavior of bromine in graphitic carbons remains unclear. In this report, using Raman spectroscopy, we reveal two types of bromine structure in graphitic carbon materials. Between fluorinated graphene layers with a composition close to C2F, Br-2 molecules are intercalated in a form similar to liquid bromine. Bromination of pristine and low-fluorinated graphitic carbons behaves very differently with distinct Br-related Raman spectra. With the guidance of density functional theory (DFT) calculations, all Raman features are assigned to normal vibration modes of specific bromine species over graphene and fluorinated graphene. When intercalated between extended non-fluorinated sp(2)-hybridized carbon regions, physisorbed Br-2 molecules move freely across the non-functionalized region toward the CF border. Multiple Br-2 molecules then combine spontaneously into Br-3-based chains, whose coupling activates otherwise Raman inactive modes. Significant charge transfer to bromine species occurs in this case. DFT calculated frequencies match precisely the experimental Br-related Raman bands observed in the intercalation carbon compounds. The fluorine-catalyzed bromine chain-formation process shown here is general and should also operate with edges and other defect species.

Graphene materials including porous few-layered graphenes are under focus of scientific community today. The great attention towards them is caused by their remarkable properties. Here, we use two different fluorinated graphite intercalation compounds with different fluorine content in their matrices to prepare thermally exfoliated fluorinated graphites and to investigate them in terms of their structural, spectroscopic and electrochemical properties as materials for use in supercapacitors. A higher temperature of low-fluorinated graphenes preparation resulted in higher exfoliation degree and higher gravimetric capacitance in supercapacitor appliances. More dramatic leap of gravimetric capacitance was observed after a treatment in a concentrated acid mixture of graphene material samples prepared at the highest temperature of thermolysis with highest exposition time.

The conductivity of few- and monolayer graphene with covalently bound moieties is a key-point in the potential application of these materials in any electrical and optoelectronic device. In particular, fluorination of such graphene-based systems is of interest, as fluorine is expected to have a strong influence on the charge-carrier density due to its high electronegativity, and therefore modify the electrical transport properties significantly. Here it is shown that, depending on the device architecture, the electrical properties of fluorinated graphene-based devices are significantly different. It is found that the conductivity of thin films of few-layer graphene decreases by several orders of magnitude with fluorine content increasing from 2.4 to 16.6 at%, whereas individual flakes show a significant increase in both conductivity and charge carrier mobility. This observation, combined with Raman microscopy study, points toward the fact that the edges of the flakes are primary sites for fluorine within the experimental range of fluorine content. The strong decrease in conductivity in the film devices is therefore associated with the high contact resistance between the fluorine saturated edges of the individual flakes.

The deintercalation process for the first stage fluorinated graphite inclusion compound C2F0.92Br0.01·0.285CH3CN was studied under isothermal conditions. It was shown by a combination of gravimetric and X ray diffraction methods that the decomposition of the first stage inclusion compound into the second stage compound (and gaseous CH3CN) under isothermal conditions proceeds through the mixed-layer state that simultaneously consists of three main microphases: the first, the second and the fourth stages of filling with their identity periods 9.42, 15.50 and 27.8 Å, respectively, and of the second stage of filling in its labile extended state with the identity period of about 16.3 Å. It follows from structural properties that the C–C bonds of “guest” molecules are mostly coplanar with the fluorocarbon layers of the “host” matrix.

The applications of multilayered graphenes (MLGs), nanocomposites “MLG–decontaminant” and polydicarbonfluoride intercalation compounds for the localization and deactivation of toxic spills and gaseous emissions under technogenic accidents are investigated in this paper. The intercalation compounds contain oxidizers as intercalants, and MLGs are formed destructively by thermolysis of polydicarbonfluoride intercalation compounds. The sorptive capacity of MLGs (about 240 ml of liquid phase per 1 g of MLG) is much higher than in well-known expanded graphites (EGs) obtained from graphite oxide or graphite acid salts. Our investigation revealed the possibility of the production of the “MLG–decontaminant” nanocomposites with the neutralizator content >95% due to the extremely low (down to 0.4 g/l) apparent density of MLG and its high specific surface (about 370 m2/g). The use of these nanocomposites for the acid–base or redox neutralization of contaminants does not result in the overheating, sputtering or evaporation of liquid phases, because their neutralization products sorb into MLGs. It prevents the soil mineralization by liquid or solid deactivated spills. We revealed that polydicarbonfluoride intercalation compounds with oxidizers (ClF3, HNO3, N2O4) can be efficiently used for the deactivation of spills and gaseous emissions of nitrogen-containing base compounds.

Tabby is a pattern of short irregular stripes, usually related to domestic cats. We have produced Tabby patterns on graphene by attaching fluorine atoms running as monoatomic chains in crystallographic directions. Separated by non-fluorinated sp 2 carbon ribbons, sp 3 -hybridized carbon atoms bonded to zigzag fluorine chains produce sp 2 - sp 3 interfaces and spin-polarized edge states localized on both sides of the chains. We have compared two kinds of fluorinated graphite samples C 2 F x , with x near to 1 and x substantially below 1. The magnetic susceptibility of C 2 F x ( x < 1) shows a broad maximum and a thermally activated spin gap behaviour that can be understood in a two-leg spin ladder model with ferromagnetic legs and antiferromagnetic rungs; the spin gap constitutes about 450 K. Besides, stable room-temperature ferromagnetism is observed in C 2 F x ( x < 1) samples: the crossover to a three-dimensional magnetic behaviour is due to the onset of interlayer interactions. Similarly prepared C 2 F x ( x ≈ 1) samples demonstrate features of two-dimensional magnetism without signs of high-temperature magnetic ordering, but with transition to a superparamagnetic state below 40 K instead. The magnetism of the Tabby graphene is stable until 520 K, which is the temperature of the structural reconstruction of fluorinated graphite.

The influence of dimensional effects on the compositions and properties of polydicarbonfluoride (C2 F)n prepared from multilayered graphenes was investigated. Multilayered graphenes were produced by destructive thermal decomposition of intercalation compounds of "idealized" (C2 F)n that were obtained by reaction of gaseous ClF3 with natural graphite at a room temperature. The precursors of multilayered graphenes have a common formula (C2 F⋅xR)n where R is an organic or inorganic component. It was shown that polydicarbonfluoride prepared from multilayered graphene does not form stable intercalation compound with ClF3 , in contrast to polydicarbonfluoride prepared from graphite, that forms its intercalation compound with ClF3 during fluorination of initial graphite in the ClF3 excess. Investigations of polydicarbonfluoride prepared from multilayered graphene showed that it cannot form intercalation compounds with different classes of organic and inorganic compounds as polydicarbonfluoride prepared from graphite can do. The absence of such intercalation activity for polydicarbonfluoride prepared from multilayered graphene can be explained by high exfoliation degree of multilayered graphene (3-4 nm) along the c-axis that results in the presence of two-dimensional (2D) structure properties in multilayered graphene. Dimensional effects transformed the chemical properties of polydicarbonfluoride prepared from multilayered graphene and lowered its decomposition temperature by 150 K in comparison with polydicarbonfluoride prepared from graphite.

Development of graphene spintronic devices relies on transforming it into a material with a spin order. Attempts to make graphene magnetic by introducing zigzag edge states have failed due to energetically unstable structure of torn zigzag edges. Here, we report on the formation of nanoridges, i.e., stable crystallographically oriented fluorine monoatomic chains and provide experimental evidence for strongly coupled magnetic states at the graphene-fluorographene interfaces. From the first principle calculations, the spins at the localized edge states are ferromagnetically ordered within each of the zigzag interface whereas the spin interaction across a nanoridge is antiferromagnetic. Magnetic susceptibility data agree with this physical picture and exhibit behaviour typical of quantum spin-ladder system with ferromagnetic legs and antiferromagnetic rungs. The exchange coupling constant along the rungs is measured to be 450 K. The coupling is strong enough to consider graphene with fluorine nanoridges as a candidate for a room temperature spintronics material.

Fluorinated graphite intercalation compounds (FGICs) with acetonitrile C2Fx · yCH3CN (x = 0.92, 0.69, and 0.49) have been synthesized using a gaseous mixture of BrF3 and Br2 at room temperature and subsequent replacement of the reaction medium components on acetonitrile by isopiestic method. The change in functional composition and electronic structure of FGICs under annealing at 250–260 °C was studied by infrared, X‐ray photoelectron, and near‐edge X‐ray absorption fine structure spectroscopy (NEXAFS) methods. Analysis of the data revealed interaction of acetonitrile with a C2Fx matrix. The X‐ray spectra detected formation of new nitrogen species attributed to two‐coordinated and mono hydrogenated three‐coordinated atoms. Mechanism of nitrogen incorporation in the fluorinated graphene layers was proposed. Schematic structure of graphite fluoride C2Fx intercalated with acetonitrile and NEXAFS N K‐edge spectrum of C2F0.69 · 0.137CH3CN before and after annealing at 250 °C.