High-resolution Transmission Electron Microscopy Techniques Research Articles

In2O3/ZnO heterostructured nanotubes: electrospinning fabrication, characterization, and highly enhanced photocatalytic properties

In2O3/ZnO heterostructured nanotubes with cubic In2O3 and hexagonal ZnO were successfully synthesized via the combination of electrospinning and calcination process. The as-prepared materials are investigated by using thermogravimetric and differential scanning calorimetry, fourier transform infrared spectroscope, X-ray diffraction, scanning electron microscope and high-resolution transmission electron microscope techniques. The formation mechanism of In2O3/ZnO heterostructured nanotubes based on the kinetics of phase separation which results from the decomposition of polyvinyl pyrrolidone during the calcination process is also discussed in detail. The photocatalytic degradation tests reveal that In2O3/ZnO heterostructured nanotubes exhibit the highly improved photocatalytic properties compared with the single-component ZnO and In2O3 materials.

Experimental Study and Calculation of the Precipitation Behavior of Carbides in Fe-5.78Cr-0.35C Alloy during High-Temperature Aging

The precipitation behavior of carbides in Fe-5.78Cr-0.35C (wt.%) alloy during aging at 850°C was studied. The type, particle size and distribution of carbides were determined and measured by the combination of HRTEM (High Resolution Transmission Electron Microscope), XRD (X-Ray Diffraction) and quantitative metallography technique. Results show that the type of carbides was M7C3 and the obvious coarsening of carbides was observed during aging. In addition, the thermodynamic and kinetic calculation using Thermo-Calc software was conducted to study the precipitation of carbides. The stable phase in the alloy aging at 850°C was M7C3 carbide and austenite which is in accordance with experimental results. According to Ostwald coarsening mechanism, the average interfacial energy between γ phase and M7C3 carbide was calculated as 0.7 J·m-2. Then the precipitation behavior of carbides in Fe-5.78Cr-0.35C alloy during aging was well predicted.

Insights into complexation of dissolved organic matter and Al(III) and nanominerals formation in soils under contrasting fertilizations using two-dimensional correlation spectroscopy and high resolution-transmission electron microscopy techniques

Understanding the organomineral associations in soils is of great importance. Using two-dimensional correlation spectroscopy (2DCOS) and high resolution-transmission electron microscopy (HRTEM) techniques, this study compared the binding characteristics of organic ligands to Al(III) in dissolved organic matter (DOM) from soils under short-term (3-years) and long-term (22-years) fertilizations. Three fertilization treatments were examined: (i) no fertilization (Control), (ii) chemical nitrogen, phosphorus and potassium (NPK), and (iii) NPK plus swine manure (NPKM). Soil spectra detected by the 2DCOS Fourier transform infrared (FTIR) spectroscopy showed that fertilization modified the binding characteristics of organic ligands to Al(III) in soil DOM at both short- and long- term location sites. The CH deformations in aliphatic groups played an important role in binding to Al(III) but with minor differences among the Control, NPK and NPKM at the short-term site. While at the long-term site both C–O stretching of polysaccharides or polysaccharide-like substances and aliphatic O–H were bound to Al(III) under the Control, whereas only aliphatic O–H, and only polysaccharides and silicates, were bound to Al(III) under NPK and NPKM, respectively. Images from HRTEM demonstrated that crystalline nanominerals, composed of Fe and O, were predominant in soil DOM under NPK, while amorphous nanominerals, predominant in Al, Si, and O, were dominant in soil DOM under Control and NPKM. In conclusion, fertilization strategies, especially under long-term, could affect the binding of organic ligands to Al(III) in soil DOM, which resulted in alterations in the turnover, reactivity, and bioavailability of soil organic matter. Our results demonstrated that the FTIR-2DCOS combined with HRTEM techniques could enhance our understanding in the binding characteristics of DOM to Al(III) and the resulted nanominerals in soils.

A novel electrochemiluminescence glucose biosensor based on platinum nanoflowers/graphene oxide/glucose oxidase modified glassy carbon electrode

A novel electrochemiluminescence (ECL) biosensor based on platinum nanoflowers (PtNFs)/graphene oxide (GO)/glucose oxidase (GODx) was discovered for glucose detection. PtNFs/GO was synthesized using a nontoxic, rapid, one-pot and template-free method and characterized by transmission electron microscopy (TEM) and high-resolution TEM techniques. The as-prepared PtNFs/GO with clean surface and multiporous structure was used to assemble GODx to form a glucose biosensor. Based on ECL results, the PtNFs/GO/GODx film-modified electrode displayed a high electrocatalytic activity towards the oxidation of glucose, which generated hydrogen peroxide (H2O2) to react with the luminol radicals thus enhanced the luminol ECL. Under the optimized conditions, two linear regions of ECL intensity to glucose concentration were valid in the range from 5 to 80 μmol/L (r = 0.9957) and 80 to 1,000 μmol/L (r = 0.9909) with a detection limit (S/N = 3) of 2.8 μmol/L. In order to verify the reliability, the thus-fabricated biosensor was applied to determine the glucose concentration in glucose injection, glucose functional drink, and blood serum. The results indicated that the proposed biosensor presented good characteristics in terms of high sensitivity and good reproducibility for glucose determination, promising the applicability of this sensor in practical analysis.

Diclofenac Sodium Adsorption onto Montmorillonite: Adsorption Equilibrium Studies and Drug Release Kinetics

The aim of the present work was to investigate the role of montmorillonite clay as an oral drug delivery carrier for in vitro controlled release of anti-inflammatory drug diclofenac sodium (DS). For this purpose, the adsorption behaviour of DS onto the clay was studied as a function of pH of the aqueous drug solution, contact time, initial drug concentration and clay dosage. The clay-drug composites synthesized were subsequently characterized by X-ray diffraction studies, Fourier transform-infrared studies, differential scanning calorimetric analysis, thermogravimetric analysis, zeta-potential measurement, scanning electron microscopic and high-resolution transmission electron microscopic techniques. A drug loading of 497 mg/g was obtained in case of intercalated clay-drug composite. The in vitro drug release studies of the synthesized clay-drug composites in simulated gastric fluid (pH 1.2) showed no release, whereas a prolonged drug release profile was obtained for the intercalated clay-drug composite i...

Thermal behaviour of natural and synthetic iron precipitates from mine drainage

TG–DTA, MS detections and XRD were used to characterize thermal behaviour of iron precipitates from acid mine drainage prepared by precipitation with urea and natural iron precipitates sampled from sludge bed (settling pit Sedem žien and old abandoned adit Hodrusa, mining area Banska Stiavnica, Slovakia). The high-resolution transmission electron microscopy and scanning electron microscopy (SEM) techniques were used to characterize the surface microstructure and shape of the synthesized and sampled iron precipitates. The SEM micrographs of the iron precipitates (natural and precipitated with urea) show that the samples had formed into agglomerates, probably due to attractive forces of quite large surface area. During heating of the all samples up to 200 °C, physically adsorbed water was removed. On further heating in the range from 250 to 350 °C in natural iron precipitates, the less stable forms (goethite, ferrihydrite, and schwertmannite) transform to more stable forms like hematite. In case of synthetic samples, the transformation runs in two steps: first in the range from 250 to 350 °C, and second in the range from 600 to 750 °C.

Synthesis and photoluminescence enhancement of PVA capped Mn2+ doped ZnS nanoparticles and observation of tunable dual emission: A new approach

This paper reports the enhanced photoluminescence (PL) property of polyvinyl alcohol (PVA) capped Mn2+ doped ZnS nanocrystals prepared by chemical precipitation method. The surface-modified Mn2+ doped ZnS nanocrystals resulted in the multi-color property. The morphology and crystallite size were characterized by field emission scanning electron microscopy (FESEM), high-resolution transmission electron microscopy (HRTEM) and X-ray diffraction (XRD) techniques. The crystallite size was estimated to be 5nm from HRTEM and calculated as 2–4nm from peak broadening of the X-ray diffraction (XRD) pattern with cubic zincblende structure. Increase in the band gap with decrease in the crystallite size was observed from the UV–visible absorption spectrum, which confirms the quantum confinement effect. The room temperature photoluminescence (PL) emission measurements revealed the presence of blue (427nm) and near IR reddish–orange (752nm) emission bands in addition to the typical yellow–orange (585nm) bands in all the Mn2+ doped samples, which were attributed due to transition within the 3ds configuration of Mn2+ ions incorporation in ZnS host under UV excitation at 320nm. As far as we know, the reddish–orange bands at 752nm near IR region along with the blue and yellow–orange colored PL are reported for the first time. In this way, the PL color from these ZnS nanocrystals can be tuned from UV to near infrared region (IR). The synthesized ZnS:Mn NPs can be further functionalized for using them as biolabels.

Iron pyrite, a potential photovoltaic material, increases plant biomass upon seed pretreatment

Iron pyrite (FeS 2 ) is a promising material with plethora of applications ranging from sulfuric acid production to photo-voltaic devices. Interestingly, the proponents of the theory of hydrothermal origin of life on earth argues that FeS 2 may have evolved 4.0 billion years ago, and used as an energy source by the earliest evolving life forms on earth. In the present time, bacteria like Thiobacillus ferrooxidans, which survives in the oxygen deficient environments, derives energy solely from FeS 2 to maintain its critical biomass. The key question, we addressed in this paper is 'whether higher plants have the ability to derive energy solely from FeS 2 , just like the way Thiobacillus species does.' To answer this question, we developed a novel, inexpensive, low temperature scheme ( 2 synthesis. We characterize FeS 2 using X-ray diffraction (XRD), scanning electron microscopy (SEM) and high-resolution transmission electron microscopy (HRTEM) techniques. Further, we pretreated the chick-pea (Legume) seeds for 12 hours in sterile, double distilled aqueous medium of dispersed FeS 2 (80 μg/ml). Following this, we allowed these seeds to grow in sterile, double distilled water for 7 days. At this stage, we observed that FeS 2 pre-treated seeds result in significantly healthier plants, with increased dryweight and enhanced sulfur content as compared to the control plants. In summary, a brief FeS 2 pre-treatment of the seeds resulted in increased plant biomass. This study has drawn an evolutionary consilience between two diverse life forms in terms of their ability to use a common pre-biotic energy molecule for biomass production. Our results suggest that FeS 2 apart from its opto-electronic potential, could also be used as a pro-fertilizer for sustainable agriculture practices.

LaxNiyOz/MAS-9 Catalysts with High Ni0 Dispersion and Hydrothermal Stability for CH4/CO2 Reforming

Mesoporous aluminosilicate (designated as MAS-9) was synthesized through assembling ZSM-5 nanocrystallites as precursors with P123 as surfactant, which exhibited excellent properties, such as large specific surface area, big pore volume, uniform pore distribution, and high hydrothermal stability. A series of LaxNiyOz/MAS-9 catalysts for CH4/CO2 reforming were prepared by the sol–gel method. Support and catalysts were characterized using N2-adsorption, X-ray diffraction, Fourier transform IR, inductively coupled plasma–mass spectrometry, H2 temperature-programmed reduction, thermogravimetric/differential scanning calorimetry, and high-resolution transmission electron microscopy techniques. The adjustment of the La/Ni molar ratio will be beneficial to the enhancement of Ni0 particle dispersion and decrease of particle size, which increased the catalytic activity and the resistance to carbon deposition. Under the condition of an atmospheric pressure at 850 °C and a gas hour space velocity of 3.2 × 104 mL·g–1·h–1, the conversion of CH4 and CO2 over LaNi2Ox/MAS-9 catalyst was 100%, and the selectivities of H2 and CO were 95% and 99%, respectively. In addition, the stability test of LaNi2Ox/MAS-9 catalyst for 145 h revealed that the conversion of CO2 (100%), the selectivity of H2 (95%) and CO (99%), with a H2/CO ratio of 0.96 as well as carbon yield (ca. 1%) almost kept constant although conversion of CH4 slightly decreased to 94%. The mesoporous structure of MAS-9 kept intact after 145 h CH4/CO2 reforming. Therefore, LaNi2Ox/MAS-9 was a promising catalyst for CH4/CO2 reforming.

Application of high-resolution transmission electron microscopy and electron energy-loss spectroscopy in the characterization of polymer nanotubes

Abstract Polyamide 6 (PA6) and polystyrene (PS) nanotubes were successfully fabricated by polymer solution-wetting method. High-resolution transmission electron microscopy (HRTEM), X-ray diffraction (XRD) and electron energy-loss spectroscopy (EELS) techniques were employed to investigate their crystallization phenomena. It has been found in HRTEM images that the crystalline lattice fringes are observed in some regions of the nanotube walls. XRD analysis showed that these two kinds of polymer nanotubes have a higher degree of crystallinity than that of the bulk materials. PA6 nanotubes dominate in γ phase while bulk PA6 present mainly in α phase. EELS has been used to determine the ratio of C=C and C-C in PS nanotubes, and our result is consistent with the theoretical calculation. HRTEM and EELS will shed light on the microstructural characterization of polymer nanotubes.

Mesoporous-structure-tailored hydrothermal synthesis and mechanism of the SrTiO3 mesoporous spheres by controlling the silicate semipermeable membranes with the KOH concentrations

Mesoporous structure-tailored SrTiO3 mesoporous spheres have been hydrothermally realized by controlling the silicate semipermeable membranes with KOH concentration. The phase and microstructures were investigated by X-ray diffraction, scanning electron microscopy, transmission electron microscopy, high-resolution transmission electron microscopy, thermogravimetric analysis and N2-physisorption techniques, respectively. Because the high KOH concentration lowers the polymerization degree of the silicate anion species, the silicate semipermeable membranes become thinner with increasing KOH concentration. Whereas the attenuated silicate semipermeable membranes favour the penetration of the metal ions, the primary SrTiO3 nanocrystallites for the self-assembly of the SrTiO3 mesoporous spheres grow larger as the KOH concentration increases. As a consequence, the mesoporous structures of the self-assembled SrTiO3 mesoporous spheres can be simply tailored by adjusting the KOH concentration of the hydrothermal reaction system. Moreover, because the attenuation of the silicate membrane facilitates the orientation attachment of the primary nanocrystallites, the self-assembled SrTiO3 mesoporous spheres trend to single-crystal-like with the increasing KOH concentration.

Fabrication and Performance of xMnyCe/Hexagonal Mesoporous Silica Sorbents with Wormhole-Like Framework for Hot Coal Gas Desulfurization

A series of xMnyCe/hexagonal mesoporous silica (HMS) sorbents with wormhole-like structure was prepared by a sol–gel method, and their performance for hot coal gas desulfurization was investigated at 600 °C. All xMnyCe/HMS sorbents exhibited high breakthrough sulfur capacity, and the utilization of these sorbents was much higher than that of 10Mn/HMS. The breakthrough sulfur capacity over 4Mn1Ce/HMS sorbents was 121.7 mg of S/g of sorbent with the utilization of 82.4%. Such a behavior was maintained in eight consecutive desulfurization–regeneration cycles. The effects of the desulfurization temperature, H2 concentration, and 7% steam on the performance of 4Mn1Ce/HMS were examined. The fresh, used, and regenerated samples were characterized by means of X-ray diffraction, N2 adsorption, Fourier transform infrared absorption spectroscopy, and high-resolution transmission electron microscopy techniques. The results confirmed that the manganese oxide was dispersed highly on the HMS support because of the syner...

The effect of Ni addition on the structure of Pt–Sn/C nanoparticles by electron microscopy

Carbon supported bimetallic Pt–Sn and trimetallic Pt–Sn–Ni nanoparticles were synthesized by Bönnemann's colloidal precursor method and characterized by high-resolution transmission electron microscopy (HR-TEM) and energy dispersive X-ray analysis (EDX) techniques. HR-TEM and EDX results demonstrated that SnO2 nanoparticles tend to form clusters in Pt–Sn/C; however, the presence of Ni in the Pt–Sn/C gives rise to an induced interaction between SnO2 and Pt nanoparticles. Electron diffraction patterns of Pt–Sn–Ni/C showed that either cubic Pt or PtSn2 structures are present. From the selected area EDX analysis, it was found that both of these structures contain Sn. This suggests that Pt–Sn–Ni/C nanoparticles may be partially covered by Sn-richer PtSn2 alloyed structure.

Study of CO and Hydrogen Interactions on Carbon-Supported Pt Nanoparticles by Quadrupole Mass Spectrometry and Operando Diffuse Reflectance FTIR Spectroscopy

CO adsorption on carbon-supported Pt nanoparticles under operando conditions was studied by quadrupole mass spectrometry and diffuse reflectance infrared fourier transform spectroscopy (DRIFTS). The Pt catalyst was also studied by high-resolution transmission electron microscopy (HRTEM), X-ray photoelectron spectroscopy (XPS), and X-ray diffraction (XRD). It was shown by HRTEM and XPS that Pt nanoparticles can be fully reduced by H2 at room temperature instead of by conventional high-temperature treatment. The Pt dispersion was determined by XRD, HRTEM, and CO chemisorption techniques with an excellent agreement among them. The room-temperature H2/O2 titration method was also used, but if assuming H/PtS = O/PtS = 1, it led to the underestimation of the dispersion compared to the other techniques. The existence of adsorption sites inaccessible to H2 (or O2) but accessible to CO because of a stronger interaction with Pt was proposed to explain the results. It was also concluded that H/Pts was lower than unity (H/Pts = 0.72) and, as a major consequence, that Pt nanoparticles with 2.7 nm diameter still have a bulk-like behavior in contrast with what was reported in the literature for 1 nm Pt particles. CO adsorption on Pt/C at 298 K after H2 treatment was studied by operando DRIFTS. The C–O stretching vibration (νCO) bands were ascribed to CO adsorbed on Pt surface at (111)-terrace, (100)-terrace, edge, and kink sites in linear and bridge forms. An unexpected νCO band at 1703 cm–1 was observed upon CO adsorption and tentatively attributed to CO on surface Pt sites interacting through its oxygen end with the carbon support. It was also shown that the adsorption of CO and H2 in successive repeated steps was necessary to reach a stable state of the adsorbed CO phase. Possible reconstruction of Pt nanoparticles at room temperature during this process is discussed.

Study of the relationship between crystal structure and luminescence in rare-earth-implanted Ga2O3 nanowires during annealing treatments

A systematical analysis of the correlation between the crystalline quality and the luminescence of rare-earth-implanted s-Ga_2O_3 nanostructures with potential applications in visible and ultraviolet photonics is presented. Europium ions led to red emission while gadolinium ions are efficient ultraviolet emitters. Different degrees of lattice recoveries of the nanostructures have been achieved after implantation by rapid thermal annealing treatments carried out at different temperatures. The recovery process has been analyzed by transmission electron microscopy (TEM), high-resolution TEM, and Raman techniques. High-fluence implantation with either of the two rare earth ions induces partial amorphization of the structures. Partial recrystallization of the nanostructures above 500 oC is revealed by Raman analysis. Nearly complete recovery of the crystal structure is obtained in the annealing temperature range 900-1100 oC, coincident with the expected value for bulk Ga_2O_3. Cathodoluminescence and photoluminescence allowed comparison of the Eu^3+ and Gd^3+ intraionic luminescence lines after annealing at different temperatures and their correlation with the crystallinity. It has been found that the width of the Eu^3+ luminescence lines clearly correlates with the width of the Raman peaks, both decreasing with annealing temperature, which shows the possibility of using the luminescence of this rare earth as a probe for lattice disorder. On the other hand, our results suggest that Gd^3+ lines are much less sensitive to disorder.

Individual Boron Nanowire Has Ultra-High Specific Young’s Modulus and Fracture Strength As Revealed by in Situ Transmission Electron Microscopy

Boron nanowires (BNWs) may have potential applications as reinforcing materials because B fibers are widely known for their excellent mechanical performance. However until now, there have been only few reports on the mechanical properties of individual BNW, and in situ transmission electron microscopy (TEM) investigations shining a light on their fracture mechanism have not been performed. In this paper, we applied in situ high-resolution TEM (HRTEM) technique to study the mechanical properties of individual BNWs using three loading schemes. The mean fracture strength and the maximum strain of individual BNWs were measured to be 10.4 GPa and 4.1%, respectively, during the tensile tests. And the averaged Young's modulus was calculated to be 308.2 GPa under tensile and compression tests. Bending experiments for the first time performed on individual BNWs revealed that their maximum bending strain could reach 9.9% and their ultimate bending stress arrived at 36.2 GPa. These figures are much higher than those of Si and ZnO nanowires known for their high bending strength. Moreover, the BNWs exhibited very high specific fracture strength (3.9 (GPa·cm(3))/g) and specific elastic modulus (130.6 (GPa·cm(3))/g), which are several dozens of times larger compared to many nanostructures known for their superb mechanical behaviors. At last, the effect of surface oxide layer on the Young's modulus, fracture strength and maximum bending strength of individual BNWs was elucidated to extract their intrinsic mechanical parameters using calculated corrections. All experimental results suggest that the present BNW are a bright promise as lightweight reinforcing fillers.

Transmission electron microscopy study of microstructural properties and dislocation characterization in the GaN film grown on the cone-shaped patterned Al2O3substrate

Growing a GaN film on a patterned Al2O3 substrate is one of the methods of reducing threading dislocations (TDs), which can significantly deteriorate the performance of GaN-based LEDs. In this study, the microstructural details of the GaN film grown on a cone-shaped patterned Al2O3 substrate were investigated using high-resolution transmission electron microscopy and weak-beam dark-field techniques. Various defects such as misfit dislocations (MDs), recrystallized GaN (R-GaN) islands and nano-voids were observed on the patterned Al2O3 surfaces, i.e. the flat surface (FS), the inclined surface (IS) and the top surface (TS), respectively. Especially, the crystallographic orientation of R-GaN between the GaN film and the inclined Al2O3 substrate was identified as $[\overline 1 2\overline 1 0]_{{\rm GaN}} \hbox{//}[\overline 1 101]_{{\rm R - GaN} \,{\rm on}\,{\rm IS}} \hbox{//}[\overline 1 100]_{ {{\rm Al}} _{\rm 2} {\rm O}_{\rm 3}} $, $(\overline 1 012)_{{\rm GaN}} \hbox{//}(1\overline 1 02)_{{\rm R - Ga}\,{\rm Non}\,{\rm IS}} \hbox{//}(\overline {11} 26)_{ {{\rm Al}} _{\rm 2} {\rm O}_{\rm 3}} $. In addition, a rotation by 9° between $(10\overline 1 1)_{{\rm R - GaN}} $ and $(0002)_{{\rm GaN}} $ and between $(10\overline 1 1)_{{\rm R - GaN}} $ and $(0006)_{ {{\rm Al}} _{\rm 2} {\rm O}_{\rm 3}} $ was found to reduce the lattice mismatch between the GaN film and the Al2O3 substrate. Many TDs in the GaN film were observed on the FS and TS of Al2O3. However, few TDs were observed on the IS. Most of the TDs generated from the FS of Al2O3 were bent to the inclined facet rather than propagating to the GaN surface, resulting in a reduction in the dislocation density. Most of the TDs generated from the TS of Al2O3 were characterized as edge dislocations.

Correlation between structure and semiconductor-to-metal transition characteristics of VO2/TiO2/sapphire thin film heterostructures

This study focuses on the role of strain and thin film epitaxy on the semiconductor-to-metal transition (SMT) characteristics of single crystalline VO2 thin films. The VO2/TiO2 heterostructures of controlled orientations were epitaxially grown on m-cut, r-cut and c-cut sapphire substrates. Detailed structural investigations were performed using high-resolution X-ray diffraction (2θ–θ and φ scans) and high-resolution transmission electron microscopy techniques to correlate SMT properties with microstructural characteristics. Monoclinic (M1) VO2 thin films with (100), (001) and (2¯01) out-of-plane orientations were grown on TiO2(101)/r-sapphire, TiO2(100)/c-sapphire and TiO2(001)/m-sapphire platforms, respectively. The in-plane alignments across the interfaces were established to be [010](100)VO2||[010](101)TiO2, [100](001)VO2||[001](100)TiO2 and [010](2¯01)VO2‖[010](001)TiO2 for r-sapphire, c-sapphire and m-sapphire substrates, respectively. We were able to tune the SMT temperature of VO2 epilayers from ∼313K to 354K (bulk Tc≈340K). The SMT characteristics were interpreted based upon the residual strain in the VO2 lattice, particularly along the c-axis of tetragonal VO2. This research introduces the VO2-based single crystalline heterostructures as a potential candidate for a wide range of applications where different transition temperatures are required.

Synthesis of a dendrimeric phenoxy-substituted cyclotetraphosphazene and its non-covalent interactions with multiwalled carbon nanotubes

A dendrimeric phenoxy-substituted cyclotetraphosphazene has been prepared for the non-covalent functionalization of multiwalled carbon nanotubes (MWCNTs). The synthesized cyclotetraphosphazene derivatives (2–4) and dendrimeric cyclotetraphosphazene (5) have been characterized by standard spectroscopic techniques. The functionalization of MWCNTs with compound 5 has been accomplished and the resulting MWCNT-5 hybrid has been characterized by 31P NMR, 1H NMR, Raman spectroscopy, X-ray diffraction (XRD), energy dispersive X-ray (EDX), fluorescence, thermal gravimetric analysis (TGA) and high-resolution transmission electron microscopy (HRTEM) techniques. The results showed that the dendrimeric compound 5 has been attached to the MWCNTs via non-covalent “π–π” interactions between the phenoxy groups on the dendrimeric compound 5 and the extended π system of the MWCNTs. The MWCNT-5 hybrid exhibited significant dispersion stability in common organic solvents.

The use of a natural Mexican zeolite as support of NiMoW sulphide hydrotreating catalysts

In order to examine the influence of type of metal precursor on the hydrodesulfurization (HDS) activity of synthetized samples, a series of ternary Ni–Mo–W catalysts supported on a natural Mexican zeolite (clinoptilolite) were prepared by sequential wet impregnation of the zeolite support with different thiosalts of W and Mo, and Ni(NO3)2·6H2O. The synthetized samples were characterized by N2 adsorption–desorption isotherms at −196°C, X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive X-ray analysis (EDX/SEM), high-resolution transmission electron microscopy (HRTEM) and X-ray photoelectron spectroscopy (XPS) techniques. The catalysts activity was evaluated in the HDS of dibenzothiophene (DBT) reaction performed in a batch reactor at 350°C and 3.1MPa of total hydrogen pressure. The activity tests demonstrated that the best catalyst was the NiMoW-H/zeo sample synthesized from ammonium thiosalts. The use of tetraalkylammonium thiometalates as metal precursors led to the decrease in the HDS activity. The most active catalyst in the HDS of DBT reaction showed the largest density of active phases on the support surface determined from HRTEM measurements.