The aim of this study is to synthesize PuO2 nanoparticles (NPs) at low pH values and characterize the materials using laboratory and synchrotron-based methods. Properties of the PuO2 NPs formed under acidic conditions (pH 1-4) are explored here at the atomic scale. High-resolution transmission electron microscopy (HRTEM) is applied to characterize the crystallinity, morphology and size of the particles. It is found that 2 nm crystalline NPs are formed with a PuO2 crystal structure. High energy resolution fluorescence detected (HERFD) X-ray absorption spectroscopy at the Pu M4 edge has been used to identify the Pu oxidation states and recorded data are analysed using the theory based on the Anderson impurity model (AIM). The experimental data obtained on NPs show that the Pu(iv) oxidation state dominates in all NPs formed at pH 1-4. However, the suspension at pH 1 demonstrates the presence of Pu(iii) and Pu(vi) in addition to the Pu(iv), which is associated with redox dissolution of PuO2 NPs under acidic conditions. We discuss in detail the mechanism that affects the PuO2 NPs synthesis under acidic conditions and compare it with one in neutral and alkaline conditions. Hence, the results shown here, together with the first Pu M4 HERFD data on PuF3 and PuF4 compounds, are significant for the colloid facilitated transport governing the migration of plutonium in a subsurface environment.

This research is focused on the adsorption modification of detonation nanodiamond surfaces with antibiotics for their further use as smart materials for cardiovascular surgery purposes, namely as bioprostheses modifiers. Tritium-labeled amikacin and levofloxacin were used as tracers for the adsorption process control. We found that nanodiamonds form adsorption complexes with levofloxacin via physical adsorption, while in the case of amikacin, electrostatic attraction contributes to the formation of more stable complexes, even in the presence of electrolytes and desorbing agents (models of biological fluids). Antimicrobial characterization of nanodiamond–levofloxacin and nanodiamond–amikacin complexes indicates a reduction in the dose of antibiotics that is used as an antimicrobial agent. Therefore, the use of biomaterial based on DND complexes with antibiotics as the basis of bioprostheses will allow one either to avoid or significantly reduce the duration and intensity of antibiotics use in the postoperative period, which is critically important from the viewpoint of the development of antibiotic resistance in pathogens.

This work is aimed at the preparation and investigation of CrOx/SiO2 catalysts of oxidative propane dehydrogenation in the presence of carbon dioxide. The mesoporous silicas used as carriers were prepared via a sol-gel method using a beta-cyclodextrin and urea mixture as a template. The amounts of water added during Si(OEt)(4) hydrolysis and chromium oxide loading were varied. The obtained catalysts were characterised via nitrogen low temperature adsorption-desorption, XRD, SAXS, SEM with EDX, TEM, XPS, UV-Vis diffuse reflectance spectroscopy and the catalytic tests. The obtained mesoporous silicas have monomodal narrow pore size distributions with the maxima at 7, 9, 10 nm increasing when the amounts of water used during the synthesis increase, and large surface areas of 680, 460, 410 m(2)g(-1), respectively. All the samples do not contain micropores. Chromium oxidation states +6 and + 3 were found according to XPS and UV-Vis diffuse reflectance spectroscopy data. The catalytic tests revealed that there is a correlation between the catalytic activity and synthesis conditions. The catalytic activity in the reaction of oxidative propane dehydrogenation in the presence of CO2 decreases in the series with a pore diameter of 9 > 10 > 7 nm. The most active and selective sample showed the selectivity to propylene up to 80% while the conversion was 20%.

Vertically aligned multi-walled carbon nanotubes (MWCNTs) are attractive for use in nanoelectronics, nanosensors, electrodes for energy storage and harvesting devices, composites, weaving yarns and many other devices. However, in order to reach practical relevance in these applications, the vertically aligned MWCNTs must be dense and sufficient height. Fulfilling those requirements is often challenging. Herein, we report production of high density vertically aligned MWCNTs with amorphous shell on iron nanoparticles by the modified CVD method in the tube flow reactor via catalytic pyrolysis of acetylene. The iron thin films of thickness from 0.5 to 68 nm were obtained by the pulsed laser deposition in droplet-free mode on single crystal silicon substrates (100). The obtained films of the thickness from 0.5 to 20 nm were arrays of nanoparticles with a size from 5 to 17 nm as a result of thermal annealing. These nanoparticles were used as catalysts for the growth of MWCNTs. SEM investigations have shown that height of the obtained vertically aligned MWCNTs depends on the thickness of the initial iron film. The height of the MWCNTs array of 42 mu m was achieved on the iron nanoparticles obtained after annealing the metal film of 5 nm thickness. The growth temperature of the obtained MWCNTs array was 700 degrees C at the volume flow ratio of the C2H2 and H2(5 %)/Ar gas mixture was 1:4. TEM investigations have shown that the diameter of the obtained MWCNTs reached 15-20 nm with amorphous shell thickness of 5-10 nm. Four distinguished Raman peaks at 1360, 1603, 2711, and 2932 cm- 1 correspond to the D-band, G-band, 2D-band, and (D + G)-band, respectively and confirm the formation MWCNTs with good graphitization.

Nanosized bimetallic PtMo, PtFe and trimetallic PtMoSn catalysts deposited on highly dispersed carbon black Vulcan XC-72 were synthesized from the cluster complex compounds PtCl(P(C6H5)3)(C3H2N2(CH3)2)Mo(C5H4CH3)(CO)3, Pt(P(C6H5)3)(C3N2H2(CH3)2)Fe(CO)3(COC6H5C2C6H5), and PtCl(P(C6H5)3)(C3N2H2(CH3)2)C5H4CH3Mo(CO)3SnCl2, respectively. Structural characteristics of these catalysts were studied using X-ray diffraction (XRD), microprobe energy dispersive spectroscopy (EDX), and transmission electron microscopy (TEM). The synthesized catalysts were tested in aqueous 0.5 M H2SO4 in a three-electrode electrochemical cells and in single fuel cells. Electrocatalytic activity of PtMo/C and PtFe/C in the oxygen reduction reaction (ORR) and the activity of PtMoSn/C in electrochemical oxidation of ethanol were evaluated. It was shown that specific characteristics of the synthesized catalysts are 1.5–2 times higher than those of a commercial Pt(20%)/C catalyst. The results of experiments indicate that PtFe/C, PtMo/C, and PtMoSn/C catalysts prepared from the corresponding complex precursors can be regarded as promising candidates for application in fuel cells due to their high specific activity.

Dendrimers are unique macromolecules composed of branched monomers that are characterized by monodispersity, biocompatibility, and multivalent surfaces and are synthesized by the stepwise addition of repetitive units. Over recent years, dendrimers have been attractive materials as detecting agents, targeting components, imaging agents, or pharmaceutically active compounds. This study demonstrates the possibility of the formation and transfer of thin sulfonimide dendrimer films of different generations to solid surfaces using the LangmuirBlodgett technique. The surface of sulfonimide dendrimers was functionalized with naphthalene end groups (from 4 to 64 groups). The developed noncovalent and covalent films showed the expected different contact angles due to the presence of the naphthyl groups attached to the dendrimer side, which can bond intramolecularly or intermolecularly. Changing the number of naphthyl groups allows control of the hydrophobic properties of the films, providing an opportunity to create two types of films with covalent and noncovalent bonding. The difference in contact angle between the 2nd and 5th generations of dendrimers was approximately 33 degrees. The low-cost formation of such transparent water-repellent film imparting water repellency to a substrate while maintaining its inherent properties, such as color and morphology, can protect glass and painted surfaces from excessive humidity.

Formation of adsorption complex between hyaluronic acid and detonation nanodiamonds was studied. Nanodiamonds that possess negative and positive zeta-potential in an aqueous suspension were used. To determine the direct amount of hyaluronic acid on the nanodiamond surface tritium label was introduced into the polymer by means of tritium thermal activation method. It was found that hyaluronic acid irreversibly adsorbs on both positively and negatively charged nanodiamonds, but in different quantities. Adsorption of hyaluronic acid on nanodiamonds of positive zeta potential leads to the isoelectric point at the surface coverage close to 100 mg/g, while further increase in surface amount of hyaluronic acid results in the formation of negatively charged particles and the increase of its species diameter comparing with the initial material. In the case of negatively charged nanodiamonds adsorption of hyaluronic acid is also observed, but it was as much as 50 times lower than in the case of positively charged nanodiamonds. Even small amounts of hyaluronic acid adsorbed on nanodiamond surface results in the disaggregation of clusters of nanodiamonds that are formed in an aqueous suspension, while zeta potential was from - 50 to - 40 mV that is around of the value for non-modified material. On the basis of the experimental data, we can suggest that the adsorption mechanism of complex formation between hyaluronic acid and nanodiamonds includes both electrostatic interaction and formation of hydrogen bonds between surface functional groups and adsorbed water molecules.

Tritium-labeled lysozyme was used to determine its adsorption on the surface of nanodiamonds produced by detonation synthesis. It was found that the amount of the adsorbed protein depends on the charge of the nanodiamond surface. A multilayer coating is formed on the originally positively charged nanodiamonds, with the adsorption becoming 4–5 times stronger on negatively charged nanodiamonds produced from the original nanodiamonds via their annealing in air. According to IR spectroscopic data, the adsorption of lysozyme results in that the number of loops and turns in the protein structure decreases in the adsorption on two types of nanodiamonds. The use of a tritium probe did not find any significant difference between the structures of protein molecules in their adsorption on nanodiamonds with different functional surface compositions. The orientation of molecules in the surface layer was found to be the same: Protein parts containing amino acid residues of phenylalanine are contacting with the sorbent, and the amino acid residues of proline, which are contained in the loops, are on the surface of the adsorption layer.

Present work is devoted to the spark plasma sintering (SPS) of multiwalled carbon nanotubes (MWCNTs), which was found to be an effective route to their compactisation. The products, obtained under different values of pressure (from 10 up to 22 MPa) and temperature (from 1000 up to 1800 degrees C), have been investigated by thermal analysis, SEM, HRTEM, Raman spectroscopy, X-Rays diffraction and low temperature nitrogen sorptometry as well as physical properties characterisation. It was found that the increase of temperature and pressure during SPS increased the density of the sintered samples and decreased their surface area. It is accompanied by appearance of the mesopores. Raman spectroscopy, TG and X-ray data show that the defectiveness of the CNTs decreased during SPS. Using a focused beam of the transmission electron microscope in-situ experimental simulation of the CNT consolidation and their crosslinking was successfully performed for the first time.

Specific features of the interaction between bismuth(iii) and hydroxyapatite (HAP) of various morphologies during its sorption and co-crystallization binding were revealed. The obtained sorption isotherms nearly coincide with each other regardless of the HAP type used and cannot be described in terms of the Langmuir or Freundlich models. Bismuth can form the intrinsic phase of bismuth phosphate due to the chemical or topochemical reaction with HAP when the sorption method is used. In the case of co-crystallization binding of bismuth ions, the morphological modification of HAP occurs. The bismuth complexes with aminopyrimidine in neutral and weakly acidic solutions are readily hydrolyzed to form a precipitate, and no binding with HAP occurs.

Extremely defect graphene oxide (dGO) is proposed as an advanced sorbent for treatment of radioactive waste and contaminated natural waters. dGO prepared using a modified Hummers oxidation procedure, starting from reduced graphene oxide (rGO) as a precursor, shows significantly higher sorption of U(VI), Am(III), and Eu(III) than standard graphene oxides (GOs). Earlier studies revealed the mechanism of radionuclide sorption related to defects in GO sheets. Therefore, explosive thermal exfoliation of graphite oxide was used to prepare rGO with a large number of defects and holes. Defects and holes are additionally introduced by Hummers oxidation of rGO, thus providing an extremely defect-rich material. Analysis of characterization by XPS, TGA, and FTIR shows that dGO oxygen functionalization is predominantly related to defects, such as flake edges and edge atoms of holes, whereas standard GO exhibits oxygen functional groups mostly on the planar surface. The high abundance of defects in dGO results in a 15-fold increase in sorption capacity of U(VI) compared to that in standard Hummers GO. The improved sorption capacity of dGO is related to abundant carboxylic group attached hole edge atoms of GO flakes as revealed by synchrotron-based extended X-ray absorption fine structure (EXAFS) and high-energy resolution fluorescence detected X-ray absorption near edge structure (HERFD-XANES) spectroscopy.

The stability of 20[Formula: see text]wt.% Co/CNT catalyst was tested in the Fischer–Tropsch synthesis and the structural transformations both in the catalyst and support were analyzed. The catalyst showed high conversion and stable selectivity during three weeks of the test, which was attributed to the optimal and stable cobalt particle size of [Formula: see text]13–14[Formula: see text]nm promoted by the support pre-oxidation. XPS, Raman, and nitrogen adsorption data revealed that the carefully chosen catalyst annealing and reduction conditions ensured the preservation of the support structure.

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The sorption of radionuclides by graphene oxides synthesized by different methods was studied through a combination of batch experiments with characterization by microscopic and spectroscopic techniques such as X-ray photoelectron spectroscopy (XPS), attenuated total reflection fourier-transform infrared spectroscopy (ATR-FTIR), high-energy resolution fluorescence detected X-Ray absorption spectroscopy (HERFD-XANES), extended X-ray absorption fine structure (EXAFS) and high resolution transmission electron microscopy (HRTEM).

In future decades, tons of silicon waste will be produced from various sources, with no reliable recycling route. The transformation of bulk silicon into SiO2 nanoparticles is significant because it provides an environmentally friendly way to recycle residual silicon waste. To address the needs of silicon recycling, we have developed a top-down approach that achieves 100% conversion of bulk silicon to silica nanoparticles with outcome sizes of 8-50 nm. In contrast to our approach, previous studies on the preparation of silica nanoparticles were based on the bottom-up method, where alkoxides served as the silicon source. In addition to silicon processing and upcycling the potential of silica, our method also possesses several advantages, such as simplicity, scalability, and controllable particle size distribution. Many fields of science and manufacturing, such as optics, photonics, medical, and mechanical applications, require size-controllable fabrication of silica nanoparticles. We demonstrate that control over temperature and hydrolysis time has a significant impact on the average particle size and distribution shape. Additionally, we unravel the process of nanoparticle formation using a theoretical nucleation model and quantum density functional theory calculations. Our results provide a theoretical and experimental basis for silica nanoparticle fabrication and pave the way for further silicon conservation research.

Adsorption of alkyltrimethylammonium bromides (DTAB, TTAB and CTAB) on detonation nanodiamonds was studied. Nanodiamonds of positive and negative zeta potentials in aqueous suspensions were used. The amount of the compound on nanodiamond surface was determined using tritium labeled surfactants. Our results suggested the same mechanism of the adsorption complex formation for nanodiamonds of total positive and negative charge.

The possibility of sorption and cocrystallization binding of lead(n) with nanohydroxyapatite (HAP) acting as a potential carrier of short-lived lead radionuclides 211,212 Pb was studied. The peculiarities of the kinetics were revealed, and the isotherms of sorption of lead ions on hydroxyapatite with different textures were constructed. A multistage sorption mechanism accompanied by a change in the structure and morphology of the sorbent was studied. The possibility of the formation of a new phase (hydroxypyromorphite) of lead during the sorption and cocrystallization interaction was shown. The introduction of lead into the synthesis of HAP at the early stages of crystallization exerts the highest effect on its morphology and structure. The optimization of the formation of the HAP-Pb composite over the course of the process will make it possible to use the short-lived 211 Pb radionuclide in subsequent experiments.

In the conservation practice of albumen photographs, wet cleaning techniques were long used to remove pollutions, gluing components, cellulose degradation products, and to reduce highlight yellowing. However, water immersion, as well as surface cleaning, enhances the cracking of the albumen layer surface. These cleaning methods are suitable for paper artworks. Whereas the conventional water treatment may cause irreversible damage of the paper structure, the use of rigid hydrogel of Gellan gum had been proposed as an alternative technique that is less destructive to the paper structure. Two wet treatments, water and Gellan gum hydrogel, were applied to the samples of original 19th century albumen photoprints. Their effect was assessed using instrumental methods, such as Fourier transform infrared spectroscopy, laser confocal microscopy, scanning electron microscopy, atomic force microscopy, and pH measurements. The effect of wet treatments on the albumen photograph surface cracking was quantified. Despite that Gellan hydrogel is very gentle and efficient tool for the restoration of paper artworks, it is as harmful for the albumen photographs surface as the conventional water surface cleaning, and therefore may be applied on the verso of the photographs solely.

Precipitates formed by the neutralisation of Pu(iii), Pu(iv), Pu(v), and Pu(vi) solutions were characterised by HRTEM, SAXS, and XRD in the suspensions. PuO2 nanoparticles uniform in size (typical diameter around 2.5 nm) and phase composition were observed in all cases under equilibrium conditions. For Pu(vi), the precipitation reactions proceed via an intermediate product.