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Search for "catalyst" in Full Text gives 328 result(s) in Beilstein Journal of Nanotechnology. Showing first 200.
Gas sensing properties of MWCNT layers electrochemically decorated with Au and Pd nanoparticles
Beilstein J. Nanotechnol. 2017, 8, 592–603, doi:10.3762/bjnano.8.64
- analyte gaseous molecules and CNTs, making their desorption difficult [11][12]. Several attempts have been made to improve the CNT-based sensor performance by modifying CNTs with polymeric composites [13], and/or catalyst metals, hybrid, and other catalytic materials [14]. Recently, a surfactant-free
- chemiresistive gas sensors by electrophoresis. This allowed for the controlled deposition of the metal content, preventing clustering formation. The gas sensing results demonstrate that the performance (e.g., sensitivity and selectivity) of the MWCNT-based chemiresistors can be controlled by the surface catalyst
Graphene functionalised by laser-ablated V2O5 for a highly sensitive NH3 sensor
Beilstein J. Nanotechnol. 2017, 8, 571–578, doi:10.3762/bjnano.8.61
- oxidation state in vanadium pentoxide (V2O5) – a good oxygen transfer catalyst that is (thermally) stable in air and vacuum [7][8][9][10]. Therefore, we considered vanadium oxide as a promising material for functionalising a graphene sensor in order to increase its selectivity towards reducing pollutant
Nanostructured carbon materials decorated with organophosphorus moieties: synthesis and application
Beilstein J. Nanotechnol. 2017, 8, 485–493, doi:10.3762/bjnano.8.52
- used is one order of magnitude lower (1% calculated on the basis of the P loading in compound 8). Further experiments aimed to evaluate the action of the catalyst in new reaction cycles revealed a fast degradation of the efficiency: the yield of amide 17 dropped to 30% and 20% in the second and third
- , oxidation to phosphine sulfide and selenide are actually under investigation in our laboratory. More significantly, we have explored the ability of one of these materials (the one with the highest loading in phosphine oxide moiety, compound 8) as heterogeneous catalyst in a Staudinger ligation reaction
- . Despite the process is still to be optimized, concerning the yield and the recycling of the catalyst, the very low amount of phosphine oxide employed make this approach promising for the development of efficient nanostructured materials useful in organocatalysis. Experimental Materials MWCNTs were
The longstanding challenge of the nanocrystallization of 1,3,5-trinitroperhydro-1,3,5-triazine (RDX)
Beilstein J. Nanotechnol. 2017, 8, 452–466, doi:10.3762/bjnano.8.49
- al. [24][25], the silica explosive gels are prepared by dissolving the energetic compound, the silica precursor and a catalyst in a co-solvent. After the gelification, an antisolvent of the explosive is injected to replace the solvent in the pores and precipitate the explosives in the silica matrix
Methods for preparing polymer-decorated single exchange-biased magnetic nanoparticles for application in flexible polymer-based films
Beilstein J. Nanotechnol. 2017, 8, 408–417, doi:10.3762/bjnano.8.43
- catalysts. Masson et al. [35] reported an increase in the styrene polymerization rate, using malonitrile as a catalyst and from initiator molecules anchored on iron oxide NPs. However, it appears that bonding the initiator to the surface through a phosphonate group limits the rate, reducing the effect of
- the catalyst. The length of the carbon backbone of the initiator (between phosphate and α-bromo-ester functions) is very important to the ATRP polymerization rate when initiators are directly anchored to the particle surface. Sunday et al. [36] reported that long alkyl chains (16 carbon atoms) or
Tailoring bifunctional hybrid organic–inorganic nanoadsorbents by the choice of functional layer composition probed by adsorption of Cu2+ ions
Beilstein J. Nanotechnol. 2017, 8, 334–347, doi:10.3762/bjnano.8.36
- comparison monofunctional samples were produced, denoted as N1 (TEOS/АРТЕS = 1:1, RT), N2, N3 and N4 (TEOS/APTES = 3:1, RT; the first with addition of first APTES, the second with first addition of TEOS, and the third with later addition of the NH3 catalyst). The labels N4i and N4h stand for carrying out the
Photocatalysis applications of some hybrid polymeric composites incorporating TiO2 nanoparticles and their combinations with SiO2/Fe2O3
Beilstein J. Nanotechnol. 2017, 8, 272–286, doi:10.3762/bjnano.8.30
- concentration as a function of irradiation time we used the Lambert–Beer law (A = ε·l·c), and the resulting plots are given in Figure 6c. It was found that the phenol degradation efficiency depends on the hybrid film employed as catalyst, and the photocatalytic performance is improved by the addition of other
- . The phenol photolysis degree under visible light in the presence of S3 and S4 films (with TiO2 and Fe2O3 NPs) is about 80% and 83%, respectively (Figure 7c). This means that the photodecomposition of phenol is similarly effective as under UV illumination if a proper catalyst is used. The apparent rate
- and S4. We must underline that the hydroquinone degradation under UV or visible light occurs faster than phenol photolysis due to the presence of two –OH groups, which yield a quicker access to catalyst. In the same time, the secondary product appearing in the system (p-benzoquinone) is almost
Nanocrystalline ZrO2 and Pt-doped ZrO2 catalysts for low-temperature CO oxidation
Beilstein J. Nanotechnol. 2017, 8, 264–271, doi:10.3762/bjnano.8.29
- were performed in order to characterize the catalyst. The calculated crystallite size of ZrO2, calculated with the help of the Scherrer equation, was around 30.3 nm. The synthesized ZrO2 was scrutinized regarding its role as catalyst in the oxidation of carbon monoxide (CO). It showed 100% CO
- oxygen mobility and oxygen vacancies and improves the activity and stability of the catalyst. The effects of gas hourly space velocity (GHSV) and initial CO concentration on the CO oxidation over Pt(1%)-ZrO2 were studied. Keywords: CO oxidation; nanomaterials; platinum; solution combustion method
- ceramic material and is widely used in the industry. It is a wide band gap semiconductor (5–7 eV) and is known for its unique mechanical, electrical, thermal, catalytic and optical capabilities [3][4]. ZrO2 finds a range of applications in different fields such as catalyst/support, as biomaterial [5], as
Nitrogen-doped twisted graphene grown on copper by atmospheric pressure CVD from a decane precursor
Beilstein J. Nanotechnol. 2017, 8, 145–158, doi:10.3762/bjnano.8.15
- with a 14 mm diameter tubular quartz reactor was employed for the experiment. Polycrystalline copper foil (99.9% purity, proved by the EDX study) with a thickness of 60 μm was used as the catalyst. Prior to the APCVD, the foil was electrochemically polished for 5 min in 1 M phosphoric acid at a bias
- consists of mechanical exfoliation, which imposes severe mechanical, uncontrolled defects in the sample. The most common and preferable is the wet-chemical etching of the catalyst (substrate). Usually a poly(methylmethacrylate) (PMMA) scaffold is applied to coat the graphene surface and support it during
- the catalyst consumption, followed by underside contaminant cleaning, then placement on the destination substrate. However, the PMMA removal from the graphene after the film transfer (which involves high-temperature Ar/H2 forming gas annealing [18], O2-based annealing [19], and in situ annealing [20
Photo-ignition process of multiwall carbon nanotubes and ferrocene by continuous wave Xe lamp illumination
Beilstein J. Nanotechnol. 2017, 8, 134–144, doi:10.3762/bjnano.8.14
- that this photo-effect occurs in air for different types of SWCNTs prepared with different methodologies and weight percent of CNTs (in the range 50–90 wt %) with respect to the Fe metal catalyst mixed with them. The authors conjectured that the ignition and combustion occur when there is a local
- traces of Fe3O4, resulting from the Fe catalyst. A TEM investigation was also performed revealing that this material is composed of two different morphologies of oxides: small nanoparticles trapped within a network of residual SWCNT bundles and large randomly interconnected or fused grains. This implies
- high-pressure carbon monoxide process from Carbon Nanotechnologies, Inc., which utilizes Fe as a growth catalyst for the SWCNTs) and Fe powder are ignited if exposed to the camera flash. Under the same conditions, the purified SWCNTs showed no reaction. The authors postulated the following theory
Sensitive detection of hydrocarbon gases using electrochemically Pd-modified ZnO chemiresistors
Beilstein J. Nanotechnol. 2017, 8, 82–90, doi:10.3762/bjnano.8.9
- chemical analyses, using scanning electron microscopy and X-ray photoelectron spectroscopy, respectively. The effect of the Pd catalyst on the performance of the ZnO-based gas sensor was evaluated by comparing the sensing results with those of pristine ZnO NRs, at an operating temperature of 300 °C and for
- Pd catalyst on the performance of ZnO-based gas sensors was investigated by the comparison of the gas sensing results of pristine and Pd-modified ZnO NRs, at an operating temperature of 300 °C, towards methane (CH4), propane (C3H8) and butane (C4H10) at a wide range of gas concentrations (30–1000 ppm
- cell. As reported in the calibration curves in Figure 4B, the sensing response of pristine and Pd-modified ZnO were strongly influenced by the presence of Pd catalyst on the surface of ZnO NRs. In Figure 5, the sensing responses of pristine and Pd-modified ZnO towards butane at different concentrations
Fundamental properties of high-quality carbon nanofoam: from low to high density
Beilstein J. Nanotechnol. 2016, 7, 2065–2073, doi:10.3762/bjnano.7.197
- solution of sucrose/naphthalene precursor leads to the formation of high-quality carbon nanofoams. The foams have uniform structure, predominantly composed of carbon microspheres. We note that our production is performed at relatively low temperatures of 150–185 °C and without a catalyst. The results show
Nanostructured SnO2–ZnO composite gas sensors for selective detection of carbon monoxide
Beilstein J. Nanotechnol. 2016, 7, 2045–2056, doi:10.3762/bjnano.7.195
- using the low cost, ecologically friendly sol–gel/dip coating method. The precursors, zinc acetate dihydrate (Merck) as a Zn2+ source and tin(II) 2-ethylhexanoate (Sigma-Aldrich), were dissolved in ethanol. Triethanolamine (Baker Analyzed) was used as a chelating agent/catalyst. The obtained solutions
Organoclay hybrid materials as precursors of porous ZnO/silica-clay heterostructures for photocatalytic applications
Beilstein J. Nanotechnol. 2016, 7, 1971–1982, doi:10.3762/bjnano.7.188
- devoted to study ZnO as a very promising catalyst in the photocatalytic degradation of water pollutants. This is because of its elevated activity, its low cost and, in particular, its environmentally friendly behavior [1][2]. It has been confirmed that ZnO compared to TiO2 exhibits better efficiency in the
- formation of silica/alumina-clay heterostructures providing acid-catalyst behavior [18][19]. Similarly, silica–titania delaminated clays have been also prepared via the generation of TiO2/SiO2 NP in the interlayer space of smectites and vermiculites modified with long-chain alkylammonium species, promoting
- of the ZnO/SiO2-clay heterostructures photocatalyst, the mixture being stirred in dark for 30 min to allow for the physical absorption of dye molecules on the catalyst particles to reach equilibrium. In the case of ibuprofen, 25 mg photocatalyst were added to 100 mL of a water solution containing 15
In situ formation of reduced graphene oxide structures in ceria by combined sol–gel and solvothermal processing
Beilstein J. Nanotechnol. 2016, 7, 1815–1821, doi:10.3762/bjnano.7.174
- –gel processing, by which the rGO structures and the catalytic activity were enhanced. Keywords: ceria; CO oxidation; graphene oxide; sol–gel processing; Introduction Ceria (CeO2) has been widely studied as catalyst or catalyst support for redox reactions owing to its high oxygen storage and release
- example, r250 °C (the reaction rate at 250 °C per gram catalyst) for rGO(0.05)–CeO2 during first heating is 1.19·10−5 changed to 8.77·10−6 mol/s·g for rGO(0.05)–CeO2–AC. This decrease is possibly caused by the removal of graphene and reduction of the surface area. The advantage of the rGO(0.05)–CeO2
Influence of hydrothermal synthesis parameters on the properties of hydroxyapatite nanoparticles
Beilstein J. Nanotechnol. 2016, 7, 1586–1601, doi:10.3762/bjnano.7.153
- management and catalyst production [13][14] because of HAp’s high sorption activity to numerous ions including several heavy metals and radionuclides [15]. A model compound reflecting bone mineral phase is a nonstoichiometric hydroxyapatite with a molar ratio different than 1.67. Nevertheless, regarding
High performance Ce-doped ZnO nanorods for sunlight-driven photocatalysis
Beilstein J. Nanotechnol. 2016, 7, 1338–1349, doi:10.3762/bjnano.7.125
- (5%) catalyst and demonstrates that the photodegradation is complete (see also Figure 8c). The ln(C/C0) plots show a linear relationship with the irradiation time, indicating that the photodegradation of Orange II occurs via a pseudo-first-order kinetic reaction ln(C/C0) = −kt, where k is the
- efficiency. Effects of Orange II and of the photocatalyst concentrations The effect of the mass of photocatalyst used for the degradation of Orange II was first evaluated (Figure 10a). Results obtained show that similar decomposition rates were obtained when using 30 or 45 mg of the catalyst (k = 0.063 and
- 0.075 min−1, respectively) while the efficiency of the photodegradation decreases when using only 15 mg of the catalyst (k = 0.027 min−1) (see Figure S5 in the Supporting Information File 1 for the plots of ln(C0/C) vs reaction time). The effect of the initial Orange II concentration (5, 10 or 20 mg/L
Fabrication and characterization of branched carbon nanostructures
Beilstein J. Nanotechnol. 2016, 7, 1260–1266, doi:10.3762/bjnano.7.116
- MWCNTs, namely Baytubes©. Other workers have shown using high resolution transmission electron microscopy (HRTEM) that Baytubes© are parallel-walled in long closed sections and that they are strong and relatively pure [27]. They form around a catalyst and are supplied as loosely agglomerated pellets
- , which results in the introduction of defects that later act as the “unzipping” points. The procedure has the additional benefit of cleaning the tubes as substantiated from the Raman (Figure 2d) and HRTEM data (Figure 3) confirming the absence of carbon impurities or residual catalyst material. The
Reasons and remedies for the agglomeration of multilayered graphene and carbon nanotubes in polymers
Beilstein J. Nanotechnol. 2016, 7, 1174–1196, doi:10.3762/bjnano.7.109
- discharge can be used to produce MWNTs with very few defects [2] and the production of large quantities is possible at low cost [127]. However, they contain a large amount of impurities such as graphite fragments, amorphous carbon, polyhedral carbon and metal catalyst particles. The carbonaceous impurities
- are removed from the arc-discharge soot usually by refluxing in HNO3 or thermal annealing in oxygen-containing atmosphere. The metal catalyst particles are removed by treatment with inorganic acids [127]. Figure 14 shows the arc discharge apparatus used by Saito and Uemura for the production of CNTs
- feedstock on catalyst particles, i.e., chemical vapor deposition (CVD) [2][36]. CNT can be produced by using organo-metallic compounds as precursor (e.g., ferrocene), a carbon feedstock (e.g., toluene) and a carrier gas (e.g., hydrogen) [130]. It is difficult to control the diameter of the nanotubes
An ellipsometric approach towards the description of inhomogeneous polymer-based Langmuir layers
Beilstein J. Nanotechnol. 2016, 7, 1156–1165, doi:10.3762/bjnano.7.107
- determined by end group titration. PLGA was synthesized by ring-opening copolymerization of rac-dilactide and diglycolide using 1,8-octanediol as an initiator and dibutyltin(IV) oxide as a catalyst. The resulting PLGA had a mean molecular weight Mn of 8300 g·mol−1, which was evaluated by GPC (universal
Manufacturing and investigation of physical properties of polyacrylonitrile nanofibre composites with SiO2, TiO2 and Bi2O3 nanoparticles
Beilstein J. Nanotechnol. 2016, 7, 1141–1155, doi:10.3762/bjnano.7.106
- batteries [21][22][23][24]. Studies on nanofibre composite mats of PAN/TiO2 have shown large photocatalytic efficiency under ultraviolet light and the potential use of these mats as catalyst in the decomposition of phenol, airborne aromatic compounds and methylene blue [25][26][27][28]. However, PAN/Bi2O3
- catalyst with the reagents, thus resulting in an increase of the effectiveness of photodecomposition processes. At an electrode distance of 20 cm we obtained composite PAN/TiO2 nanofibres with diameters smaller by approx. 40%, than to those obtained in [34], and by 78% smaller than the diameters of
Multiwalled carbon nanotube hybrids as MRI contrast agents
Beilstein J. Nanotechnol. 2016, 7, 1086–1103, doi:10.3762/bjnano.7.102
- transformations [18]. Surprising results of the relaxation effects both in vitro and in vivo and depending on a number of parameters, such as content of the residual catalyst, size of the CNTs or "wrapping media" (the electrolyte used to stabilize the dispersions), were also reported [18][19]. We discuss these
- vapor deposition (c-CVD) [20]. This is the most common method of MWCNT synthesis. The inherent consequence of the application of a metal catalyst (e.g., ferrocene, aluminum oxide) is the presence of a nanometallic deposit in the tubes [21]. Thus obtained MWCNTs are already an interesting scaffold for
- materials, oMWCNT#Maciejewska, were investigated by Maciejewska [18]. A different catalyst (ferrocene) percentage (2 wt %, 5 wt %, 10 wt %) in the c-CVD procedure resulted in corresponding residual iron contents of 3.9, 5.8 and 12.4 wt %, as well as in varying diameters of 29, 49 and 40 nm, respectively
Selective photocatalytic reduction of CO2 to methanol in CuO-loaded NaTaO3 nanocubes in isopropanol
Beilstein J. Nanotechnol. 2016, 7, 776–783, doi:10.3762/bjnano.7.69
- mixture and reduced CO2 using pure water as an electron donor. The activity was quite high for both H2 and CO production, achieving 20× (H2) and 7× (CO) higher than that of the cubic sample prepared by the solid state reaction. This was an indication that the catalyst morphology played a crucial role in
- ][25][26][27]. Isopropanol was employed as both an absorber and a sacrificial reagent due to its good capability to absorb CO2 and donate electrons [28][29][30]. Acetone, an important industrial material, was generated as the oxidation product of isopropanol. Experimental Catalyst preparation Tantalum
- % CuO loading on NaTaO3, respectively. Catalyst characterization The catalysts were characterized by X-ray diffraction (XRD, Bruke/D8-Advance, Cu Kα radiation, λ = 0.154056 nm) at a scanning rate of 4°/min ranging from 15° to 70°. The morphology was observed with a Hitachi S-4800 field emission scanning
Facile synthesis of water-soluble carbon nano-onions under alkaline conditions
Beilstein J. Nanotechnol. 2016, 7, 758–766, doi:10.3762/bjnano.7.67
- , Damanhour, Egypt 10.3762/bjnano.7.67 Abstract Carbonization of tomatoes at 240 °C using 30% (w/v) NaOH as catalyst produced carbon onions (C-onions), while solely carbon dots (C-dots) were obtained at the same temperature in the absence of the catalyst. Other natural materials, such as carrots and tree
- absence and in presence of 30% (w/v) NaOH. We discovered that the use of NaOH as catalyst favored the formation of C-onions when tomatoes were used as C-source and that intermediate carbon nanostructures were formed when carrots or tree leaves were used. On the basis of the morphologies and spectral
- buckling patterns of C-onions [23]. To the best of our knowledge, the results shown here, demonstrate for the first time, the possibility of obtaining C-onions from green C-sources just by modifying the carbonization conditions using sodium hydroxide as catalyst. Figure 4 represents the XRD pattern of the
Hemolysin coregulated protein 1 as a molecular gluing unit for the assembly of nanoparticle hybrid structures
Beilstein J. Nanotechnol. 2016, 7, 351–363, doi:10.3762/bjnano.7.32
- order to prove the catalytic performance of the gold hybrid structures, they are used as a catalyst in the reduction reaction of 4-nitrophenol showing similar catalytic activity as the pure Au NPs. To further extend the functionality of the Hcp1_cys3 gluing unit, Fe3O4 and CoFe2O4 NPs are aligned in a
- to a higher squareness value of the hysteresis curve. Thus the Hcp1_cys3 unit is shown to be very versatile in the formation of new biohybrid materials with enhanced magnetic, catalytic and optical properties. Keywords: gold catalyst; hemolysin coregulated protein 1 (Hcp1); magnetic hybrid materials
- nanomaterials. Furthermore, kinetic investigation of the formation of such 1D Au NP structures and the utilization of this structure, for example, as a SERS template and catalyst are also of great interest. The formation kinetics of Au NP networks triggered by Hcp1_cys3 is investigated using UV–vis spectroscopy
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