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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.

Certain limitations of obtaining metal nanoparticles with the use of synthetic chemicals have sparked a great interest in scientists to develop green synthesis procedures which use non-toxic and eco-friendly reagents and wastes. Essential oils have the potential to simultaneously act as reducing agents and stabilizers for the synthesis of metal nanoparticles. In the present work, we have synthesized gold nanoparticles (AuNPs) using clove oil (Syzygium aromaticum L. essential oil) as the main reducing agent and stabilizer. The AuNPs solutions were characterized by UV–VIS spectroscopy, and the isolated solid AuNPs were analyzed by Fourier transformed infrared spectroscopy. Various reactivity descriptors determined in terms of Conceptual Density Functional Theory, for the 16 predominant components of clove oil, have been calculated by using the quantum chemical B3LYP/6-311G** level of theory. With the aim to validate the chosen theoretical method, the calculated infrared spectra have been compared with the available experimental spectra. Moreover, the active centers for nucleophilic and electrophilic attacks have been identified through the analysis of atomic partial charges and Fukui function indices. The obtained theoretical results should be considered as a starting point for the prediction of the appropriateness of essential oils for the direct green synthesis of metal nanostructures.

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.

In the present work, we report, for the first time, the production of stable nanocolloids of highly monodisperse silver and gold nanoparticles (AgNPs and AuNPs) using phytosynthesis approach. With the aim to eliminate misinterpretations associated with the use of usually applied crude plant extracts, the presented study was focused on the use of polyphenolic fraction isolated from elderberry fruits (Sambucus nigra L.) for the synthesis. Obtained AgNPs and AuNP were characterized by UV–Vis and FTIR spectroscopy, DLS and TEM. We observed unexpectedly high capability of the natural polyphenols not only to form monodisperse nanoparticles but also to stabilise the concentrated nanocolloids (539 mg/L AgNPs and 739 mg/L AuNPs) for at least two years. Moreover, AgNPs showed strong antibacterial properties against pathogenic bacterial strains Staphylococcus aureus and Escherichia coli (inhibited after 15 min and totally stopped growth after 3 and 5 h at 3.125 mg/L concentration).

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.

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.

The surface of microporous Norit® GAC 830 W carbon was fluoroalkylated by heating in 1,1,1,2-tetrafluoroethane and 1,1,1,2,2-pentafluoroethane at 400 and 500 °C. Elemental analysis, FTIR ATR spectroscopy, and TG studies showed the presence of ∼0.1–0.7 mmol g−1 of the fluorine-containing groups. Nitrogen adsorption measurements and quenched solid density functional theory simulations proved an increase in the mesoporosity. By combining the results of solid-state 19F NMR and XPS analyses, we determined the functionalization of the carbon surface with CF, CF3, and CF2 fluorine-containing groups. Supercapacitor electrodes prepared from these materials were subjected to the charge-discharge tests and electrical impedance measurements. During galvanostatic cycling in the aqueous 30% KOH, they showed an enhanced charge capacitance compared to the parent (830 W) and the reference (Supra 30) carbons. These observations suggest that the fluoroalkylated surface and the modified microporous structure have an additive effect on capacitance parameters of carbon electrodes studied in symmetric, negative and positive modes. The fluoroalkylation caused an increase in the surface capacitance up to 38%. Herein, we demonstrate the fluoroalkylation is a simple way to increase a capacitance of carbon electrodes.

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.

International audience; A novel sensing system was designed for pH measurements based on the enhanced and quenched photoluminescence (PL) and UV–Vis absorption of the diluted water solutions of F-, O-, and N-containing carbon nanoparticles (FON-CNPs). These FON-CNPs were solvothermally synthesized, dissolved, ultra-filtrated, and separated by thin-layer chromatography. The total fluorine content in them was found to be 1.2–1.5 mmol per gram. Their TGA showed a total weight loss of 52.7% because of the thermal decomposition and detachment of the surface groups and the partial burning of the functionalized shell on the carbon core at temperatures below 1200 °C. TEM and Raman data confirmed the presence of graphitic structures in the carbon core. From the results of ATR FTIR and UV–Vis spectroscopies, we showed that a carbon shell incorporates different functional groups covering the carbon core. The surface groups of the carbon shell include carboxyl, phenolic, and carbonyl groups. Heterocyclic N-containing and amino groups and trifluoromethyl groups supporting the hydrophobicity were also found. We suggested the possible reasons for the pH responses obtained with the sensing system considering them dependent on the de-protonation of functional groups with pH change.

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.

The structure of a newly synthesized 3-methylthio-4-phenyl-5-phenylamino-1,2,4-triazole 1 and its hexabromotellurate salt 2 was investigated. The X-ray diffraction study of 2 gives the insight on the different interaction types in the crystal. The DFT calculations were used for the comprehensive study of the intramolecular and intermolecular forces that are present in the title 3-methylthio-4-phenyl-5-phenylamino-1,2,4-triazole hexabromotellurate. The presence of three different aromatic moieties in the investigated compounds cause π-π stacking interactions which were studied through the Hirshfeld surface analysis and with the discrimination of weak interaction types by filling color to a reduced density gradient (RDG) function isosurface. The RDG in the crystalline state was calculated upon experimental molecular geometry by partitions of the crystal to QM part that was calculated at M06-L/6-311G(d,p) level, and the semi-empirical QM part that was modeled with the PM7 method in QM/MM-like manner. The reactivity of 3-methylthio-4-phenyl-5-phenylamino-1,2,4-triazole and its protonated form was also discussed in terms of conceptual DFT theory and it shows the tendency of sulfur to be the most active center in an electrophilic and radical attack, whereas the site for nucleophilic substitution is medium dependent and not an unequivocal. NICS(1) index was used for the analysis of aromaticity of three different cyclic moieties. The present study insights the changes in the structure of a polyfunctional substituted triazole upon its protonation and explains these changes with the analysis of weak interactions.

The synthesis of a new hexabromotellurate of triazole ring-containing amino acid is described. XRD, NMR and DFT analysis of the structure of protonated [(5-amino-4-phenyl-4H-1,2,4-triazol-3-yl)sulfanyl]acetic acid testifies the protonation of the first nitrogen atom of the triazole ring. Hirshfeld surface analysis identifies numerous intermolecular interactions in the newly synthesized organic-inorganic hybrid hexabromotellurate. The DFT based comprehensive analysis of the structures of possible conformers also testifies the higher thermodynamic stability of the 1-protonated triazole cation, whereas the starting [(5-amino-4-phenyl-4H-1,2,4-triazol-3-yl)sulfanyl]acetic acid exists in solution in neutral form with the intermolecular hydrogen bond between the carboxylic acid OH group and the second nitrogen of the triazole ring. The experimentally observed NMR upfield shift of the signal of the exocyclic amino group was studied via GIAO computations and was explained through the analysis of the HOMOs of the neutral and protonated forms of the triazole compound.

A new cetylpyridinium picrate ionic liquid has been synthesized and characterized by differential thermal analysis, XRD, FT-IR, and NMR (1H and 13C) spectroscopy. Differential thermal analysis indicates the congruent melting of cetylpyridinium picrate and a temperature range of liquid state is 47–267 °C. A solid form of the sample characterized with a polymorphic transformation at 37 °C, which was confirmed via the XRD analysis. The interionic charge-transfer interactions, namely the charge transfer from the picrate anion to the cetylpyridinium cation, were detected by comparison of NMR spectra of DMSO solutions of the ionic liquid and cetylpyridinium chloride. The H–NMR chemical shifts’ differences of about 0.2 ppm and 0.1 ppm were observed in the case of the o-protons and the α-methylene group protons, respectively. Additionally, the charge-transfering between the attracted ions was confirmed by DFT calculations. Based on the solid state NMR technique, the higher ions mobility was suggested for the solid sample of the ionic liquid in comparison to the solid cetylpyridinium chloride monohydrate. Moreover, the association constants KA at 22, 30, 40, and 50 °C, obtained from the electrical conductivity measurements, clearly testifies much lower dissociation in the case of picrate. The KA values of cetylpyridinium picrate and chloride in DMSO medium at 22 °C equal 748.7 L/mol and 525.0 L/mol, respectively. The performed DFT computations of the reduced density gradient function in four proposed structures of the new ionic liquid cation-anion pair identifies the presence of weak non-covalent C H•••O N interactions between cetyl chain hydrogen atoms and nitro groups of picrate was explored through DFT calculations and analysis of the RDG function.

We propose a facile route for the surface functionalization of activated carbons (ACs), which are used as a solid matrix with good mechanical properties, but have the deficiency of the active surface sites to form the AC-based solid acids (ACSA) by the direct chemical method. The route includes three stages that provide active and stable strong acidic surface layer. The surface chemistry changes at the functionalization stages were controlled with thermogravimetric (TG) and thermoprogrammed desorption (TPD) methods. N2 adsorption-desorption studies demonstrate the conservation of the AC meso- and macroporosity. According to XPS, DRIFT, TG-TPD-IR, and potential titrimetry data, the ACSA obtained by sulfonation of the styrene functionalized AC are contained up to 1.1 mmol g−1 of the strong acidic SO3H groups. The surface functionalization, as reported route, gives no prominent structural changes, from XRD data, the large macropores and transport channels maintain, from SEM data, and MicroRaman spectra show no defecting of the initial carbon matrix. The obtained ACSA are effective catalysts for the dehydration of 2-propanol and combine the high efficiency of work with the increased thermal stability of the surface layer. The thermoresistance of the ACSA significantly exceeds that of the Amberlyst-15 WET catalyst.

A few different theoretical methods for assigning the partial atomic charges were benchmarked for calculation of the hydrophilic/lipophilic index (HLI). The coefficients were selected to produce the best correlation of the HLI values with the experimental octanol-water partition. Different parameters were checked in calculations of partial charges to get the best performance of the HLI values obtained. Thus, four partitioning schemes (Coulson, Mulliken, Merz-Kollman, Ford-Wang) were benchmarked for calculations of atomic charges with six semiempirical methods (AM1, PM3, RM1, PM6, PM6-D3H4, PM7). Moreover, five distinct types of partial atomic charges (Mulliken, Hirshfeld, Löwdin, CHELPG, NPA), obtained at the Hartree-Fock and DFT levels of theory with three basis sets, were tested for their ability to produce the HLI values with the best correlation to experimental logP coefficients of 50 mono-charged organic anions. In the case of the semiempirical methods, the best correlation between the HLI and logP values (the correlation coefficient r = 0.9216) was obtained with the AM1 Ford-Wang parametric electrostatic potential charges. The Mulliken and Coulson charges calculated with the PM7 method can be used as an alternative to AM1, with the r values of 0.9107 and 0.8984, respectively. In the case of the DFT, the PBE/def2-TZVP natural population analysis charges produce the best correlation (r = 0.9220). Nevertheless, in spite of a marginally lower performance (r = 0.9159), the NPA charges computed at the PBE/def2-SVP level are more robust and can be regarded as the optimum choice for calculating the HLI values. Graphical abstract The hydrophilic/lipophilic index (HLI).

In this study, natural microporous activated carbon (AC) was barothermal treated with hydrogen peroxide vapors at 553 and 623 K. Nitrogen adsorption proves the formation of micro-mesoporous ACs with S ext of 350 m2 g−1 at S BET = 1250 m2 g−1. The texture of ACs drastically depends on the oxidant concentration and temperature at the treatment. Thermal behavior of the initial and obtained ACs was examined in an argon dynamic atmosphere with thermogravimetric (TG) analysis. Thermoprogrammed desorption coupled with infrared spectroscopy (TPD-IR) and MS spectroscopy monitoring of evolved gases were used to disclose the regularities of the surface groups thermodestruction. TG-TPD-IR shows that the barothermal oxidation suppresses the rich surface chemistry of the initial AC, of 1 mmol g−1 of oxygen-containing functional groups. The oxidation causes selective functionalization of the AC surface with 2.6–4.3 mmol g−1 of non-acidic quinolic (Qu) groups. The CO/CO2 release from the barothermal treated ACs has reached the Boudouard equilibrium at temperatures above 930 K. Thermal stability of two different surface centers, single spaced and vicinal Qu groups, is assigned as a factor responsible for issues related to the thermodesorption of CO/CO2 and the passage of the reversed reaction of Boudouard–Bell.