Chemical catalysis by colloids and clusters

Lewis, Lionel S.

doi:10.1021/cr00024a006

Cited by 1,412 publications

(696 citation statements)

References 95 publications

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“…For G4-OH(Pt 40 ) and G4-OH(Pt 60 ) particles, the metal particle diameters are 1.4 ( 0.2 and 1.6 ( 0.2 nm, which are slightly larger than the theoretical values of 1.1 and 1.2 nm, respectively, calculated by assuming that particles are contained within the smallest sphere circumscribing a fcc Pt crystal. X-ray energy dispersive spectroscopy (EDS) and X-ray photoelectron spectroscopy (XPS) analyses were also carried out, and they unambiguously identify the particle composition as zerovalent Pt.…”

Section: Scheme 1 Schemementioning

confidence: 63%

“…4,11,12 That is, the dendrimer acts as a selective nanoscopic filter that controls the catalytic activity of the composite. For example, the TOFs for G6-OH(Pd 40 ) and G8-OH(Pd 40 ) are only 10% and 5%, respectively, of that of G4-OH(Pd 40 ) for N-isopropyl acrylamide. However, when the same materials are used to reduce the linear alkene, a much smaller decrease in activity is noted.…”

Section: Encapsulatedmentioning

confidence: 99%

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Dendrimer-Encapsulated Metal Nanoparticles: Synthesis, Characterization, and Applications to Catalysis

et al. 2000

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This Account reports the synthesis and characterization of dendrimer-encapsulated metal nanoparticles and their applications to catalysis. These materials are prepared by sequestering metal ions within dendrimers followed by chemical reduction to yield the corresponding zerovalent metal nanoparticle. The size of such particles depends on the number of metal ions initially loaded into the dendrimer. Intradendrimer hydrogenation and carbon-carbon coupling reactions in water, organic solvents, biphasic fluorous/ organic solvents, and supercritical CO 2 are also described.

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Section: Scheme 1 Schemementioning

confidence: 63%

Section: Encapsulatedmentioning

confidence: 99%

Dendrimer-Encapsulated Metal Nanoparticles: Synthesis, Characterization, and Applications to Catalysis

et al. 2000

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“…The particle synthesis and the subsequent size selection using solvent-pair precipitation techniques are described in detail elsewhere. 16,19,20 All particles were selectively precipitated up to four times, and were characterized by x-ray powder diffraction and ultraviolet/visible ͑UV/vis͒ absorption spectroscopy. More extensive characterizations of these particles are described elsewhere.…”

Section: ͓S0003-6951͑97͒03123-9͔mentioning

confidence: 99%

“…We have recently shown that metal nanocrystals on a Langmuir trough may be compressed into any one of a number of phases, depending on the applied pressure and the chemical details of particle-particle interactions. 16 Such broad control over the properties of nanocrystal thin films, coupled with electrical measurements, should provide a powerful route toward fabricating single-electron devices. Also, phenomena related to particle composition as well as interparticle interactions may be investigated.…”

mentioning

confidence: 99%

Parallel fabrication and single-electron charging of devices based on ordered, two-dimensional phases of organically functionalized metal nanocrystals

Markovich

Leff

Chung

et al. 1997

Applied Physics Letters

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A parallel technique for fabricating single-electron, solid-state capacitance devices from ordered, two-dimensional closest-packed phases of organically functionalized metal nanocrystals is presented. The nanocrystal phases were prepared as Langmuir monolayers and subsequently transferred onto Al-electrode patterned glass substrates for device construction. Alternating current impedance measurements were carried out to probe the single-electron charging characteristics of the devices under both ambient and 77 K conditions. Evidence of a Coulomb blockade and step structure reminiscent of a Coulomb staircase is presented. © 1997 American Institute of Physics. ͓S0003-6951͑97͒03123-9͔The study of solid-state devices based on single-electron tunneling has been an intense area of research over the last decade. [1][2][3] One promising route to the fabrication of such devices is the use of nanometer-size metal and semiconductor particles as the active device elements. 4-8 Solution-phase chemical methods for synthesizing these passivated metal 9,10 and semiconductor nanocrystals 11,12 have rapidly evolved over the past few years. For single-electron device applications, recent work has indicated that passivated nanocrystals of coinage metals may be particularly useful. 8 Also, singleelectron energy level spacings in metal particles are dominated by simple electrostatics, and may be readily tuned through the modification of nanocrystal size. For sufficiently small (ϳ2 -4-nm-diam) particles, the single-electron charging energies that characterize a particle are much greater than kT at room temperature, suggesting the possibility of operation of metal nanocrystal-based single-electron devices at ambient temperature.A major challenge associated with incorporating nanometer-size particles into electronic devices in any parallel fabrication technique is related to the preparation of uniform thin films consisting of narrow size distributions of nanocrystals. Granular metal films and heteroepitaxially grown quantum dot islands are two possibilities, and indeed much important work has been done using these techniques. 6,7,13,14 However, control over particle size, size distribution, and particle density, in general, is nontrivial 15-17 especially for particles below 10 nm in diameter.One alternative is to use a Langmuir trough to prepare a film of nanocrystals and to transfer that film to a substrate. 18 This technique has certain advantages. Particle size and composition ͑i.e., the nature of the metal and the surface passivant͒ are selected prior to film deposition, and the film may be transferred to virtually any substrate of any size. We have recently shown that metal nanocrystals on a Langmuir trough may be compressed into any one of a number of phases, depending on the applied pressure and the chemical details of particle-particle interactions. 16 Such broad control over the properties of nanocrystal thin films, coupled with electrical measurements, should provide a powerful route toward fabricating single-electron devices. ...

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“…This study includes the quick formation of Au and Au-Ag alloy nanoparticles and understanding the surface plasmon resonance peaks (SPR) [18,19] of the nanometal and nanometal alloys [20,21]. This work is an extension of our earlier work on the synthesis of biomaterials, employing a UV-vis spectrophotometer.…”

Section: Introductionmentioning

confidence: 99%

Biosynthesis and stabilization of Au and Au–Ag alloy nanoparticles by fungus,Fusarium semitectum

Sawle

Salimath

Deshpande

et al. 2008

Science and Technology of Advanced Materials

105

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Crystallized and spherical-shaped Au and Au-Ag alloy nanoparticles have been synthesized and stabilized using a fungus, F. semitectum in an aqueous system. Aqueous solutions of chloroaurate ions for Au and chloroaurate and Ag + ions (1 : 1 ratio) for Au-Ag alloy were treated with an extracellular filtrate of F. semitectum biomass for the formation of Au nanoparticles (AuNP) and Au-Ag alloy nanoparticles (Au-AgNP). Analysis of the feasibility of the biosynthesized nanoparticles and core-shell alloy nanoparticles from fungal strains is particularly significant. The resultant colloidal suspensions are highly stable for many weeks. The obtained Au and Au-Ag alloy nanoparticles were characterized by the surface plasmon resonance (SPR) peaks using a UV-vis spectrophotometer, and the structure, morphology and size were determined by Fourier transform infrared spectroscopy (FTIR), x-ray diffraction (XRD), and transmission electron microscopy (TEM). Possible optoelectronics and medical applications of these nanoparticles are envisaged.

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Chemical catalysis by colloids and clusters

Cited by 1,412 publications

References 95 publications

Dendrimer-Encapsulated Metal Nanoparticles: Synthesis, Characterization, and Applications to Catalysis

Dendrimer-Encapsulated Metal Nanoparticles: Synthesis, Characterization, and Applications to Catalysis

Parallel fabrication and single-electron charging of devices based on ordered, two-dimensional phases of organically functionalized metal nanocrystals

Biosynthesis and stabilization of Au and Au–Ag alloy nanoparticles by fungus,Fusarium semitectum

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