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In this study, we considered changes in the surface chemistry after introducing fluorine into the surface layer of nanoporous activated carbon (BAU) produced from the birch wood. Here, we examined the BAU treated with 1,1,1,2-tetrafluoroethane at the selected temperature in the range of 400–800 °C. Diverse methods, including chemical analysis, nitrogen adsorption–desorption, SEM–EDS, XPS, and 19F solid-state NMR, were used for the characterization of the prepared materials. It was found that one can introduce from 0.17 to 0.42 mmol of F per gram of BAU using fluoroalkylation at 400–500 °C. Increasing the temperature to 600 °C increases the fluorination efficiency, and the relatively high fluorine content of 1.86 mmol of F per gram of BAU can be reached. At least three group types, namely, C–F, CF2, and CF3 groups, were found by XPS and 19F solid-state NMR after such treatment. The content of “semi-ionic” fluorine drastically increases in the surface layer after high-temperature fluoroalkylation at 700 °C and 800 °C. This “semi-ionic” fluorine, in the form of C–F and CF2 groups, is directly conjugated with the π-electron system of the carbon matrix.

Here we report on the application of Mentha piperita L. extract mediated synthesis of gold nanoparticles (AuNPs) with a response in the infrared range. Chromatographic studies showed the extract of M. piperita contains secondary metabolites typically acting as reducing and stabilizing agents. To shed light on the kinetic regularities of the phytosynthesis, we examined the formation of Au nanocolloids in situ considering the impact of the content of reagents: the extract (0.25 mg/ml of dry matter) and HAuCl4 (0.025–0.975 mM) were investigated in the time range 1–75 min. The formation of non-spherical AuNPs is confirmed by TEM and UV–Vis characterization of nanocolloids. UV–Vis spectroscopy showed surface plasmon resonance peaks at 534 and > 900 nm drifting into the infrared range with time and composition of reacting mixtures. The sizes of AuNPs according to the protocol varied from 10 to near 200 nm. TEM showed pseudo-spherical, triangular, and hexagonal AuNPs. Non-ideal surface relief by AFM data for large triangular and hexagonal AuNPs and structural imperfections from HRTEM studies are demonstrated. Kinetic studies showed S-shaped kinetic curves for the reaction of HAuCl4 and the plant extract. All effective constants found for the process of NPs forming can be explained by the more intense formation of large AuNPs and by the formation of NPs of a different shape with a different absorption spectrum at the same time.

Medium-temperature fluoroalkylation of microporous activated carbons (ACs) with 1,1,1,2-tetrafluoroethane is presented. Supercapacitor (SC) electrodes based on the fluoroalkylated ACs showed enhanced specific capacitance and high specific energy in electrolytes, either aqueous potassium hydroxide solution or tetraethylammonium tetrafluoroborate-acetonitrile solution. We found the largest increase in the specific capacitance, up to 89 F g–1, and in the specific energy, up to 7.5 Wh kg–1, at the voltage of 1.5 V. The specific capacitance of the SC electrode based on the sample prepared at 350 °C increases by a factor of ~ 2–3 × for certain scan rates in the organic electrolyte. The fluoroalkylated ACs have good electrochemical stability in the tested model systems. We associate the registered enhanced SC parameters with an increase in the total fluorine content and high specific surface areas of the carbon electrode materials. The surface “isolated fluorine” formed during fluoroalkylation at 300–400 °C ensures the production of improved electrode materials for SC applications. Fluoroalkylation is a simple and cost-effective method of improving the specific capacitance of carbon-based SC electrodes.

Based on the asymmetric diblock copolymer (DBC) poly(ethylene oxide)/polyacrylic acid, effective, biocompatible and biodegradable micellar carriers were obtained for the delivery of vitamin E analogue, α-tocopheryl acetate (α-TOCA), in living organisms. The monitoring of the stability of micellar structures of the block copolymer and its composition with α-TOCA over time, in a saline solution and when the pH of the solution changes, was carried out. The stability of DBC micelles over time at pH = 3.5, partial disaggregation of micelles at pH = 9 and an increase in their aggregation in physiological solution were shown. The high stability of the α-TOCA/DBC composition formed in situ in time in the range of pH=3.5-9 and a significant decrease in its solutions of salting out effects in the presence of NaCl were established. The thermodynamic parameters of the process of the micelle formation of the pure α-TOCA in water/ethanol solution (95/5 v/v) as well as the size and morphology of its micellar structures were determined by light scattering and TEM methods. The initial α-TOCA micelles in water/ethanol solution were stable over a wide pH range, but their stability was much lower and the sensitivity to the presence of NaCl was much higher than that of DBC micelles. The dialysis method revealed the gradual release of the drug from the micellar carrier through a semipermeable membrane into the surrounding aqueous and aqueous-saline media. However, the rate and efficiency of α-TOCA release from the DBC micelles in an aqueous medium were significantly lower compared to a similar process of drug release from the pure α-TOCA dispersion. Thus, a possibility of providing of long-term controlled release of α-TOCA in the living organism due to the use of DBC micelles has been proven. Based on in vivo tests of the biological action of the composition on pregnant sows, its high bioavailability, rapid absorption, active participation in metabolic processes and positive effect on the reproductive qualities of sows compared to pure α-TOCA, were displayed, which improves the safety and productivity of newborn piglets. Key words: diblock copolymer, α-tocopheryl acetate, micellar carrier, encapsulation/release, biological action.

In the present article, we reported the application of the extract of leaves from Solidago canadensis L. for the green synthesis of triangular and hexagonal gold nanoparticles (AuNPs). The phytochemical characterization, by reaction with HAuCl4 solutions, showed that the extract of Solidago canadensis L. contained the secondary metabolites that can act both as reducing and as stabilizing agents. For the synthesis of AuNPs, the effects of the HAuCl4 concentration (0.25–0.975 mM) and the reaction time (10–180 min) were investigated. The formation of AuNPs is confirmed by the color change from yellowish to purple-red. Photoluminescence measurements of Au nanocolloids showed a continuous emission band ranging from violet to red. UV–Vis characterization of AuNPs in the prepared nanocolloids showed surface plasmon resonance peaks at 530 and > 870 nm. TEM revealed that the AuNPs are in the range of 8–200 nm, they have spherical, triangular, and hexagonal forms of varying sizes. AFM and STM showed a non-ideal relief of large triangular and hexagonal gold nanoprisms. The EDX analysis, XRD and SAED patterns confirmed the face-center cubic structure of AuNPs.

Nanoporous activated carbon (NAC) beads that prepared by carbonization of microporous polymer 2,6-di-tert-butyl pyridine beads were subjected to bromination followed by amination to synthesize the ...

Multi-walled carbon nanotubes (MWCNTs) have an ordered geometric structure, large specific surface area, prominent electrical conductivity, and unique mechanical properties. They are nontoxic and c...

In the present article, we showed the effect of ultrasonic treatment on the thermal oxidation of detonation nanodiamonds (DNDs) by considering the kinetic aspect of their thermal stability in the air, in the framework of the classical Arrhenius approach. Nanostructures and surface chemistry of the pristine, ultrasonicated, and oxidized DNDs were studied by miscellaneous physical techniques to clarify the origin of the effect. Ultrasonic treating decreases the heterogeneity of aggregated nanoparticles and removes admixtures and non-diamond carbon from the surface interface of nanodiamond grains. After thermal oxidation that followed ultrasonication treatment, the size-reduction of nanodiamond crystals caused the annihilation of nitrogen-vacancy centers and led to photoluminescence quenching. Because the number of surface defects reacting with air oxygen decreases after the ultrasonic treatment, the thermal stability of DND nanopowders towards oxidative treatment shows an increase.

Because of the low content of chelating groups onto carbon fibers (CFs), their adsorptive parameters are poor, and this has negative effects on their applications as lightweight sorbents. In this work, we established a modification method to incorporate amine groups into carbon fiber surfaces by bromination followed by ammonolysis to create an interfacial layer which can adsorb heavy metal ions from solutions. The changed chemical composition, surface morphology, and thermal stability were investigated. Thermoprogrammed desorption mass-spectrometry and thermal analysis showed thermal transformation and interplay between forms of the grafted bromine groups of 0.5 mmol/g and the resulting amino groups of 0.44–0.56 mmol/g. After grafting, the surface chemistry parameters were improved due to the covalent bonding and grafting of the amine groups as interface modifier. Scanning electron microscopy observation also confirmed that the surface morphology maintains the same, without impairment of fiber properties. This work is therefore a beneficial approach towards enhancing the adsorption parameters by controlling the interface layer of CFs.

The functionalization of the carbon fiber based on polyacrylonitrile with sulfur-containing groups of high acidity was carried out in order to obtain the acid-base processes catalysts. Fibers were treated with sulfur vapors in the temperature range of 400-800°C, followed by surface oxidation with 30% hydrogen peroxide solution. Modified samples were investigated by chemical analysis, thermo-programmed desorption with mass spectrometric registration of products, IR spectroscopy and thermogravimetry. It is shown that the obtained materials contain SO3H-functional groups and oxygen-containing groups (carboxyl, lactone, phenolic, etc.) formed in the surface layer during the oxidation of the fiber surface. The chemical analysis showed that the concentration of sulfur in the samples of the modified fiber is 1.6-6.5 mmol/g. The synthesized samples have a satisfactory thermal stability. The synthesized catalysts were investigated in the model reaction - gas phase dehydration of isopropyl alcohol. It was found that obtained SO3H-containing carbon fibers were catalytically active and had high propylene selectivity. For all the samples obtained there is a complete conversion of alcohol into propylene. The activity of modified carbon fiber samples in the reaction indicated is a fairly high, temperatures of the total conversion of alcohol into propylene are in the range of 160-190°C. During the study of synthesized catalysts in several cycles of catalysis it have been shown that within repeated use (3 cycles) of all modified fiber samples, the yield of propylene does not decrease, the activity remains stable - the temperature of the dehydration reaction remains unchanged or increases insignificantly (by 5-10ºС). The temperatures of complete conversion of isopropyl alcohol in propylene for synthesized catalysts are lower than the temperatures of destruction maxima of surface sulfogroups. Thus, modified carbon fibers can be used as low-temperature catalysts of acid-base processes, in particular dehydration of alcohols.

Here, we have examined the nanoporous activated carbon fibers (ACFs) sulfonated using the direct sulfonation and the staged method that included bromination, followed by sulfidation and oxidation. TEM confirmed the nanoporous structure of the prepared sulfonated ACFs. Nitrogen porometry and 2D nonlocal DFT simulations showed the nanoporosity reduction and variations of the pore size distribution because of the functionalization. Comparison of parameters of the SO3H groups confined in nanopores, e.g., the thermal stability and catalytic potential, showed that the most efficient acid sites, in the catalytic 2-propanol dehydration to propylene, are the SO3H groups grafted by the staged Houben–Weil methods. From the productivity of reactions used at the preparation stage, and in contrast to the one-staged aromatic substitution, the bromine addition to π sites of the edges of carbon matrix supplies enough active sites and is a reason for further high yields of the grafted thermostable SO3H groups. Hydrolysis of the grafted bromine and the surface oxidation of nanopores walls are parallel reactions that lowered the SO3H-related acidity, increasing the total acidity to 1.5 mmol g−1. The reported nanoporous sulfonated ACFs are effective to be used in the dehydration reactions catalyzed by solid acids.

In this study, we report the green synthesis of gold nanoparticles (AuNPs) with the use of easily available, safe to handle juniper extract (Juniperus communis L.) as a reducing and stabilizer agent. The AuNPs were characterized by UV–Vis absorption spectroscopy, atomic force microscopy (AFM), and transmission electron microscopy (TEM). Their growth was examined by UV–Vis spectroscopy over 24 h during storage at room temperature. Absorption measurements showed that the plasmon resonance wavelength appears around 530 and 700 nm. Electron-dispersive X-ray analysis (EDX) and selected area electron diffraction (SAED) of AuNPs evidenced the presence of Au (fcc) phases. TEM analysis showed spherical AuNPs and gold triangular nanoprisms. Differences in size and shape of the AuNPs were observed. ATR–FTIR confirmed the typical functional groups of polyphenols and their oxidation products on the AuNPs’ surface.

Oxidation of activated carbon (AC) with nitric acid was carried out, and the resulting AC/HNO 3 showed high capacity when used as supercapacitor electrode material operated in the KOH electrolyte. Oxidation caused different structural changes in the AC, reducing the specific surface area and the total pore volume. After oxidation, the content of all types of oxygen-containing groups and, especially, carboxyl groups showed a significant increase. Despite the significant reduction of the specific surface area, the specific capacitance of the oxidized AC in symmetric supercapacitor electrodes is 1.4 times larger than that for the pristine AC.

Multi-walled carbon nanotubes (MWCNTs) were functionalized with residues of either 3-sulfolene or diethyl acetylenedicarboxylate through the Diels-Alder reaction. The structure of the functionalized MWCNTs was characterized by Fourier-transform infrared spectroscopy and by nitrogen adsorption with pore size analysis using the Density functional theory models. Thermogravimetric analysis in an inert atmosphere demonstrates the presence of the grafted pendant groups, which can be active centers for future effective functionalization.

Bromination and oxidation are concurrent reactions that passed on the surface of carbon solids and carbon nanomaterials. In this study, their products were modeled for a hexagonal carbon network that forming a honeycomb 2D planar structure made of sp2-hybridized bonded carbon. Two types of active centers, namely, HC=CH and C-H groups linked to peripheral zigzag carbon atoms, were considered during the DFT simulations. The oxidation process is more advantageous than bromination. Free active centers, even that on the oxidized surface, maintain their ability to the bromine addition reaction. However, the probability of their existence on the oxidized surface is very low. The active centers of the surface can be renewed by the removal of oxygen-containing groups at thermal treatment in an inert atmosphere.

Nanoporous activated carbon fibers (BusofitTM, BACF) showed effective adsorption of carbon tetrachloride (CTC) vapors. About 2.50 mmol × g−1 of chlorine, in the form of trichloromethyl and ...

In this work, the adsorption of copper ions onto activated carbons that oxidatively modified with H 2 O 2 and HNO 3 was studied. The prepared sorbents with the surface area of 275–780 m 2 /g contain 0.53–3.77 mmol/g of oxygen-containing groups. It was found that the oxidized activated carbon effectively adsorbs Cu 2+ ions from aqueous solutions. For the most efficient activated carbon–HNO 3 –30 sorbent, the percentage removal of copper ions from solutions of varying concentration is high. In the concentration range from 1.5 to 6 × 10 −4 M of Cu 2+ , it reaches >55%. At the concentrations lower than 1.5 × 10 −4 M, the expected removal is above 80%. The experimental equilibrium adsorption data were modeled with 2- and 3-parameter isotherms. The analysis of adsorption modeling results accounting for the surface heterogeneity effect was provided. The data fit well to the Dubinin–Radushkevich model. Presumably, the complexation of Cu 2+ with oxygen-containing groups passes within micropores. We found the correlation between the sorption capacity for Cu 2+ and the concentration of surface groups. The presence of the carboxyl, anhydride, and lactone groups make a major impact on the adsorption.

For the first time, a contactless express method, which is based on the self-action of picosecond range laser pulses at 1064 nm, is used for the characterization of an optically dense porous layer of carbon material (CM) bulk particles obtained from a lignocellulosic source. It is found that the oxidation treatment reduces the Brunauer–Emmett–Teller (SBET) surface area from 9.52 × 105 m2/kg to 2.73 × 105 m2/kg. This reduction occurs due to the destruction of the carbon matrix fraction and to the formation of novel O-containing surface groups. The concentrated 30-mass% HNO3 is found to be the most efficient oxidant giving the highest yield of carboxylic (Cb), anhydridic, lactonic, and phenolic surface functionalities. The concentration of the surface functional groups is determined in a dynamic argon atmosphere by thermogravimetric (TG) analysis and thermoprogrammed desorption coupled with IR (TPD-IR) spectroscopy. The surface acidity defined from data of the Boehm titration shows the acceptable agreement with the data of TG-TPD-IR examination. An enhancement of the surface hydrophilicity allows the use of carbon matrix for the covalent binding of bioligands, amino acids, their residues, and proteins to the oxygen-containing functionalities, such as Cb groups. The observed photoinduced absorption efficiency of the bulk carbon particles Im(X(3)C) ∼ 10−16 m2/W is in the range of that of nanosized carbons. A slight variation of the ratio Im(X(3)C)/SBET within the limits of experimental errors indicates a certain correlation between the absorptive NLO response and the CM specific surface. We suggest to utilize Im(X(3)C) as a quality parameter for carbon materials subjected to the oxidation, which is a typical initial step of the most commonly used functionalization routes for the preparation of biomedical materials., Вперше було застосовано швидкий безконтактний метод, який базується на самовпливi пiкосекундного лазерного випромiнювання на довжинi хвилi 1064 нм, для характеризацiї оптично густих пористих шарiв об’ємних частинок карбонових матерiалiв (КМ), що отриманi з лiгноцелюлозної сировини. Показано, що окислювальна обробка призводить до зменшення площi поверхнi Брунауера–Еммета–Тейлора (SBET) вiд 9,52 · 105 м2/кг до 2,73 · 105 м2/кг, яка вiдбувається за рахунок руйнування частини вуглецевої матрицi та формування нових О-вмiстних поверхневих груп. Найбiльш ефективним окиснювачем виявлено концентровану HNO3 30 мас.%, яка приводить до найефективнiшого утворення карбоксильних, ангiдридних i лактонних, та фенольних поверхневих груп. Концентрацiю таких функцiональних груп було визначено в динамiчнiй атмосферi аргону за допомогою термогравiметричного аналiзу (ТГ) i термопрограмованої десорбцiї, що поєднується iз IЧ (ТПД–IЧ) спектроскопiєю. Кислотнiсть поверхнi, яка визначалася за даними титрування за Бьомом, добре узгоджується iз даними ТГ–ТПД–IЧ дослiджень. Пiдвищення гiдрофiльностi поверхнi дозволяє застосовувати вуглецеву матрицю для ковалентного зв’язування бiолiгандiв, амiнокислот, їх похiдних та протеїнiв з кисневмiсними функцiональними карбоксильними групами. Отриманi значення ефективностi фотоiндукованого поглинання Im(X(3)C) ∼ 10−16 м2/В добре збiгаються з вiдповiдними для нанорозмiрних КМ. Показано, що вiдношення Im(X(3)C)/SBET є майже сталим у межах експериментальної похибки. Це вказує на певну кореляцiю мiж абсорбцiйним нелiнiйно-оптичним вiдгуком та питомою поверхнею КМ. Ми пропонуємо використати Im(X(3)C) як параметр якостi карбонових матерiалiв в процесi їх окиснення. Окиснення є типовим початковим кроком найпоширенiших методiв функцiоналiзацiї КМ для бiомедицинських застосувань.

In this study the nonlinear optical response of porous μm sized carbonaceous particles (cp) was studied within the self-action of 42 ps laser pulses at 1064 nm. Photoinduced absorption efficiency (PAE) of air-thin layer of cp was examined versus the total surface area of cp. The porous thin layer shows predictably discrete response, depending on the level of the surface oxidation. Surprisingly, the ratio between PAE and the surface area show a constant trend within the experimental error range. This observation makes NLO response a promising regulator could be used in metrology of related bulk porous materials.

The present study is objected to develop an analytical remote optical diagnostics of the functionalized carbons surface. Carbon composites with up to 1 mmol g−1 of irreversibly adsorbed bromine were produced by the room temperature plasma treatment of an activated carbon fabric (ACF) derived from polyacrylonitrile textile. The brominated ACF (BrACF) was studied by elastic optical scattering indicatrix analysis at wavelength 532 nm. The obtained data were interpreted within results of the thermogravimetric analysis, X-ray photoelectron spectroscopy and temperature programmed desorption mass spectrometry. The bromination dramatically reduces the microporosity producing practically non-porous material, while the incorporated into the micropores bromine induces the dielectric and structural impact on surface polarizability and conductivity due to the charging effect. We have found that the elastic optical scattering in proper solid angles in the forward and the backward hemispheres is sensitive to the kind of the bromine bonding, e.g., physical adsorption or chemisorption, and the bromination level, respectively, that can be utilized for the express remote fabrication control of the nanoscale carbons with given interfaces. Electronic supplementary material The online version of this article (doi:10.1186/s11671-017-1873-7) contains supplementary material, which is available to authorized users.