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  • Articles  (22)
  • nanoparticles
  • 2010-2014
  • 2005-2009
  • 2000-2004  (22)
  • Technology  (12)
  • Chemistry and Pharmacology  (10)
  • Geosciences
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  • Articles  (22)
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  • 1
    Electronic Resource
    Electronic Resource
    Detecting palladium nanoparticles in Pd/C catalysts using X‐ray Rietveld method (2000)
    Springer
    Catalysis letters 64 (2000), S. 119-124 
    Details
    ISSN: 1572-879X
    Keywords: Pd/C catalysts ; nanostructural features ; nanoparticles ; nanoclusters ; X‐ray diffraction ; Rietveld analysis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract This study uses X‐ray diffraction (XRD) techniques to investigate the nanostructural features of a series of four Pd/C catalysts, which had the same load, 0.51 ± 0.02 wt%, as palladium, with significantly different dispersions, obtained by applying different temperature ageings up to 873 K. By means of a Rietveld refinement, performed using a special fitting procedure, which takes into account the various contributions to the background scattering, the palladium fraction due to nanoparticles or clusters smaller than about 20–25 Å could be determined. We have compared this Rietveld (absolute) quantitative method with a simpler, but less precise, single‐peak (relative) XRD analysis, interesting for fast industrial applications. The Pd fractions due to nanoparticles, as determined by the two methods, are close each other for all samples investigated, apart from one for which the disagreement is near 20%.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1019080213448
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  • 2
    Electronic Resource
    Electronic Resource
    Adsorbate-induced restructuring and pressure-dependent adsorption on metal nanoparticles studied by electron microscopy and sum frequency generation spectroscopy (2000)
    Springer
    Topics in catalysis 14 (2000), S. 3-14 
    Details
    ISSN: 1572-9028
    Keywords: platinum ; palladium ; alumina ; silica ; nanoparticles ; electron microscopy ; sum frequency generation ; carbon monoxide ; adsorption ; vibrational spectroscopy ; high pressure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Several examples are presented that illustrate how the internal and surface structure of oxide supported Pt nanoparticles can change under reaction conditions. High temperatures and the presence of adsorbates may lead to different effects: (1) changes in the particle size distribution (sintering or redispersion) that may affect the crystallographic and electronic structure of the nanoparticles, (2) restructuring of the particle surface facets, and (3) crystallization of large polycrystalline aggregates. Three different model systems are described that are well-suited for high resolution transmission electron microscopy (HRTEM) and/or surface science techniques. To examine the influence of high gas pressure on the structure of adsorbates, infrared-visible sum frequency generation (SFG) surface vibrational spectroscopy is applied to monitor CO adsorption on supported Pd nanoparticles from 10-7 to 200 mbar. The adsorption site occupancy of CO, in particular the on-top population, strongly depends on pressure and temperature preventing a simple extrapolation of low pressure results to reaction conditions.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1009094613850
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  • 3
    Electronic Resource
    Electronic Resource
    The flexible surface or the rigid surface? (2000)
    Springer
    Topics in catalysis 14 (2000), S. 85-94 
    Details
    ISSN: 1572-9028
    Keywords: catalysis ; metal surfaces ; oxide surfaces ; nanoparticles ; spillover ; SMSI ; oxygen storage ; STM
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract In this paper we discuss aspects of the concept described by Somorjai as the “flexible surface”, and whether some surfaces can be considered to be inflexible, or rigid. We present STM results which appear to manifest both types of behaviour for surfaces, depending on their oxidation state. Copper metal surfaces can be classed as flexible, showing facile reconstruction in the presence of oxygen, whereas an oxidised Pd(110) surface shows no apparent diffusivity, even at 500 K. We go on to show data for a bulk oxide which indicates that sub-stoichiometry in the sample induces an element of flexibility in the surface, especially during reaction with oxygen. Finally, this is related to the direct observation of spillover on model catalysts of Pd nanoparticles supported on TiO2. It must be recognised that flexibility relates to surface diffusivity and hence length- and time-scales. Surfaces which appear inflexible at short times may be flexible at long times. In relation to catalysis then, surface flexibility depends on the relationship between the time-scale of diffusive events on the surface and the catalytic turnover number.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1009011217485
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  • 4
    Electronic Resource
    Electronic Resource
    Instrumentation and Measurement Issues for Nanometer Particles: Workshop Summary (2000)
    Springer
    Journal of nanoparticle research 2 (2000), S. 103-112 
    Details
    ISSN: 1572-896X
    Keywords: nanoparticles ; measurements ; instrumentation ; standards ; aerosols ; colloids
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics , Technology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1010025905861
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  • 5
    Electronic Resource
    Electronic Resource
    White-light Detection for Nanoparticle Sizing with the TSI Ultrafine Condensation Particle Counter (2000)
    Springer
    Journal of nanoparticle research 2 (2000), S. 85-90 
    Details
    ISSN: 1572-896X
    Keywords: nanoparticles ; pulse height analysis ; aerosol ; particle size ; condensation particle counter ; light scattering
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics , Technology
    Notes: Abstract Several of the most common methods for measuring nanoparticle size distributions employ the ultrafine condensation particle counter (UCPC) for detection purposes. Among these methods, the pulse height analysis (PHA) technique, in which the optical response of the UCPC detector is related to initial particle diameter in the 3–10 nm range, prevails in applications where fast sampling is required or for which concentrations of nanoparticles are frequently very low. With the PHA technique, white light is required for particle illumination in order to obtain a monotonic relationship between initial particle diameter and optical response (pulse height). However, the popular, commercially available TSI Model 3025A UCPC employs a laser for particle detection. Here, we report on a novel white-light detection system developed for the 3025A UCPC that involves minimal alteration to the instrument and preserves normal counting operation. Performance is illustrated with pulse height spectra produced by differential mobility analyzer (DMA) – generated calibration aerosols in the 3–50 nm range.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1010042604201
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  • 6
    Electronic Resource
    Electronic Resource
    Particularities of Heat Conduction in Nanostructures (2000)
    Springer
    Journal of nanoparticle research 2 (2000), S. 199-204 
    Details
    ISSN: 1572-896X
    Keywords: nanoscale heat transfer ; nanoparticles ; nanowires ; phonons ; superlattices ; thermal conductivity ; thin films ; microscale effects
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics , Technology
    Notes: Abstract Heat conduction in nanostructures differs significantly from that in macrostructures because the characteristic length scales associated with heat carriers, i.e., the mean free path and the wavelength, are comparable to the characteristic length of nanostructures. In this communication, particularities associated with phonon heat conduction in nanostructures, the applicability of the Fourier law, and the implications of nanoscale heat transfer effects on nanotechnology are discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1010003718481
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  • 7
    Electronic Resource
    Electronic Resource
    Hetero-Colloidal Metal Particle Multilayer Films Grown Using Electrostatic Interactions at the Air–water Interface (2000)
    Springer
    Journal of nanoparticle research 2 (2000), S. 183-190 
    Details
    ISSN: 1572-896X
    Keywords: superlattices ; colloidal particles ; Langmuir–Blodgett films ; electrostatic complexation ; air-water interface ; nanoparticles
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics , Technology
    Notes: Abstract The formation of nanoparticle multilayer films by electrostatic immobilization of surface-modified colloidal particles at the air–water interface has been recently demonstrated by us. In this paper, we extend our study to show that multilayer assemblies consisting of metal particles of different chemical nature (hetero-colloidal particle superlattices) and size can be deposited by the versatile Langmuir–Blodgett technique. Multilayer films consisting of a different number of bilayers of gold and silver colloidal particles have been deposited and characterized using quartz crystal microgravimetry and UV–visible spectroscopy measurements. It is observed that while layer-by-layer deposition of the different colloidal particle assemblies is possible by this technique without a detectable variation in the cluster density in the different layers, a degree of post-deposition reorganization of the clusters occurs in the film. In addition to this aging behavior, the effect of different organic solvents on the reorganization process has also been studied.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1010060419378
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  • 8
    Electronic Resource
    Electronic Resource
    Nanochemistry – Chemical Reactions of Iron and Benzene Within Molecular Clusters (2000)
    Springer
    Journal of nanoparticle research 2 (2000), S. 147-155 
    Details
    ISSN: 1572-896X
    Keywords: benzene ; nanoclusters ; ion chemistry ; lasers ; mass spectrometry ; nanoparticles
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics , Technology
    Notes: Abstract Molecular clusters represent a nanoscale test tube where chemical reactions can be examined in a unique way for the effects of the local environment and the possibility of size-dependent reactions. Previous experiments have shown that the ionization/dissociation of iron pentacarbonyl clusters can lead to the formation of iron ions and iron cluster ions and that these species can further react with dopant molecules to yield chemically rearranged products. The present experiments characterize similar reactions with benzene molecules and clusters. Heteroclusters of the form [Fe(CO)5]m(C6H6)nArp are created in an expanding supersonic jet of the component molecules. Following ionization by a 30 ps, 266 nm laser pulse, extensive dissociation, aggregation, and chemical rearrangement occurs leading to ionic products which are characterized by mass spectrometry. Cluster ions of the type Fem(C6H6)n + are observed as products. The stability of the sandwich form of the ion, Fe(benzene)2 +, is inferred from the data. Evidence for a similar special stability for the double-decker, Fe2(benzene)3 +, is presented.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1010034122603
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  • 9
    Electronic Resource
    Electronic Resource
    Nanoparticles as Antituberculosis Drugs Carriers: Effect on Activity Against Mycobacterium tuberculosis in Human Monocyte-Derived Macrophages (2000)
    Springer
    Journal of nanoparticle research 2 (2000), S. 165-171 
    Details
    ISSN: 1572-896X
    Keywords: tuberculosis ; nanoparticles ; antituberculosis drugs ; Mycobacterium tuberculosis ; drug delivery
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics , Technology
    Notes: Abstract This is the first report evaluating the nanoparticle delivery system for three antituberculosis drugs: isoniazid, rifampin, and streptomycin. The typical particle size is 250 nm. We studied accumulation of these drugs in human monocytes as well as their antimicrobial activity against Mycobacterium tuberculosis residing in human monocyte-derived macrophages. Nanoparticle encapsulation increased the intracellular accumulation (cell-association) of all three tested drugs, but it enhanced the antimicrobial activity of isoniazid and streptomycin only. On the other hand, the activity of encapsulated rifampin against intracellular bacteria was not higher than that of the free drug.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1010061013365
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  • 10
    Electronic Resource
    Electronic Resource
    Influence of Hydrothermal Temperature on Structures and Photovoltaic Properties of SnO2 Nanoparticles (2000)
    Springer
    Journal of nanoparticle research 2 (2000), S. 309-313 
    Details
    ISSN: 1572-896X
    Keywords: hydrothermal synthesis ; nanoparticles ; surface photovoltage ; spectroscopy ; surface state
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics , Technology
    Notes: Abstract Two SnO2 nanoparticles were synthesized by hydrothermal method at 170 °C and 180 °C, respectively. Transmission electron microscope observations reveal that the diameters of both the nanoparticles are around 6 nm. At the same time, surface photovoltage spectroscopy measurements show that the nanoparticle synthesized at 180 °C has more surface electronic states at 0.3 eV below the conduction band than the one synthesized at 170 °C. This means that the temperatures chosen in hydrothermal synthesis have significant influence on the surface electronic characteristics of resultant SnO2 nanoparticles but the effect on their sizes is not obvious. However, after being calcined at 500 °C for 2 h, the diameter of the nanoparticle synthesized at 180 °C increased to 23 nm and that of the nanoparticle synthesized at 170 °C increased to 32 nm as calculated from X-ray diffraction pattern.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1010015111781
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