Colloidal catalysis: the effect of sol size and concentration

Freund, Paul L.; Spiro, M.

doi:10.1021/j100253a007

Cited by 154 publications

(163 citation statements)

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“…Forty years ago Frens mentioned a steep decrease of NP" size by a factor 6 when X is varied from 0.8 to 2. This size decrease has been confirmed by several studies [8,[27][28][29][30][31][32][33] together with the concomitant decrease of the polydispersity. Surprisingly, the experimental results obtained in quite similar conditions are conflicting for X  3 ( Figure 1) where the polydispersity is yet minimized.…”

Section: Introductionsupporting

confidence: 74%

“…[Au III ], [27,28] X, [8,[27][28][29][30][31][32][33] [DCA], [15,17,18,20] [electrolyte] [34] , pH, [15,19,24] temperature [35,36] , initiation method [37] ) that enable to obtain, eventually in high quantity, AuNPs with radius ranging between 2 and 75 nm with narrow size and shape polydispersity. Among these parameters the reactant ratio, X, is the oldest and probably the most exploited to modify AuNPs size.…”

Section: Introductionmentioning

confidence: 99%

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Shape-Tailored Colloidal Molecules Obtained by Self-Assembly of Model Gold Nanoparticles with Flexible Polyelectrolyte

Shi

Carn

2015

Langmuir

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ABSTRACT.We study the effect of citrate to gold molar ratio (X) on the size of citrated gold nanoparticles (AuNPs). This dependence is still a matter of debate for X  3 where the polydispersity is yet minimized. Indeed, there is no consensus between experiments proposed so far for comparable experimental conditions. Nonetheless, the sole available theoretical prediction has never been validated experimentally in this range of X. We show unambiguously using 3 techniques (UV-Vis spectroscopy, dynamic light scattering and transmission electronic microscopy), 2 different synthetic approaches (Direct, Inverse) and 10 X values for each approach that AuNPs' size decay as a monoexponential with X. This result is, for the first time, in agreement with the sole available theoretical prediction by Kumar et al. on the whole studied range of X.2

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Section: Introductionsupporting

confidence: 74%

Section: Introductionmentioning

confidence: 99%

Shape-Tailored Colloidal Molecules Obtained by Self-Assembly of Model Gold Nanoparticles with Flexible Polyelectrolyte

Shi

Carn

2015

Langmuir

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“…Nanocatalysis has attracted great attention in the past two decades, both in heterogeneous solution-phase colloidal reactions [1][2][3] and in heterogeneous supported nanoparticle gas-phase reactions. 3,4 Our group published a Science report early on showing that platinum nanoparticles can be synthesized in a variety of shapes 5 (tetrahedral, cubic, and truncated octahedral).…”

mentioning

confidence: 99%

A New Catalytically Active Colloidal Platinum Nanocatalyst: The Multiarmed Nanostar Single Crystal

et al. 2008

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Nanocatalysis has attracted great attention in the past two decades, both in heterogeneous solution-phase colloidal reactions [1][2][3] and in heterogeneous supported nanoparticle gas-phase reactions. 3,4 Our group published a Science report early on showing that platinum nanoparticles can be synthesized in a variety of shapes 5 (tetrahedral, cubic, and truncated octahedral). In that report, it was suggested that catalysis could be shape-dependent, and since that time the field has developed extremely rapidly. 6-9 Narayanan and El-Sayed 6 later showed that, indeed, the activation energy of the nanocatalyzed electron-transfer reaction between thiosulfate and hexacyanoferrate III is shape-dependent in colloidal nanocatalysis in which nanocatalysts that have more atoms on edges or corners (i.e., more valency unsaturated atoms) possess more catalytic activity. More recently, shape-dependence was also found to occur in heterogeneous gas-phase nanocatalysis. 7,8 Furthermore, we found that the catalytically active nanoparticles undergo shape changes to the less active nanospheres, causing them to lose some of their activity. [10][11][12] The possible mechanism for shape change and particle growth was recently discussed where the high-resolution TEM images were reported. 13 Previously, 14 tetrahedral platinum nanoparticles have been prepared by the hydrogen reduction technique, and different sizes were synthesized by changing the ratio of the preprepared platinum seed concentration to the Pt +2 concentration. Very recently in a Science report, 3 tetrahexahedral platinum nanocrystals with high index facets, i.e., rich in active valency unsaturated atoms, have been synthesized electrochemically. The authors showed that they are also catalytically very active. These particles were prepared and studied on the surface of an electrode and were not transferable to colloidal solutions.In the present work, tetrahedral platinum nanocrystals (TPNs) were used as seeds for the preparation of a new shape of a colloidal platinum nanostar, without the need for organic solvents, templates, ion replacements, or substrates. The TPNs used were themselves synthesized in large yields by a simple new technique. The lowand high-resolution TEM of the nanostar particles are determined, and the number of arms on each nanostar is found to vary from particle to particle, ranging from a few to over 30. More interesting is that even the largest nanostars are found to form single crystals. This strongly suggests a mechanism of formation involving seeded growth rather than an aggregation or an assembly process of the seed particles. The catalytic activity for these multiarmed nanostar platinum single crystals is examined for the reaction between hexacyanoferrate III (HCFIII) and thiosulfate and found to be higher than the platinum TPN, which are known to be the most active shape of this metal in colloidal solutions.To prepare the tetrahedral platinum nanocrystals (TPNs), 0.0667 g of PVP (MW 360 000) was dissolved in 33 mL of deionized water, 4 drops of...

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“…The higher catalytic activity of the polygonal gold nanoparticles was attributed to them having a greater number of sharp edges and corners. Freund and coworkers reported the catalytic activity of citrate-stabilized Au nanoparticles in the reaction between ferricyanide and thiosulfate ions [114] . The catalytic rate increased with an increase in the concentration of the Au nanoparticles, suggesting that the catalytic rate was proportional to the surface area of Au nanoparticles.…”

Section: Synthetic Catalysismentioning

confidence: 99%

Surfactant-free solution-based synthesis of metallic nanoparticles toward efficient use of the nanoparticles’ surfaces and their application in catalysis and chemo-/biosensing

Kawasaki

2013

Nanotechnology Reviews

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Abstract:The choice of stabilizer and the stabilizer-toprecursor ions molar ratio during metal nanoparticle synthesis are important for controlling the shape, size, and dispersion stability of the nanoparticles. However, the active sites on the nanoparticles surfaces may be blocked by the stabilizing agents used, resulting in a less-than-effective utilization of the surfaces. In this review, various surfactant-free solution-based methods of synthesizing metal nanoparticles are described, along with the applications of such nanoparticles in catalysis and sensing. " Surfactant-free " synthesis does not imply truly bare metal nanoparticles synthesis but implies one where the metal nanoparticles are prepared in the absence of additional stabilizing agents such as thiolate and phosphine compounds, surfactants, and polymers. These metal nanoparticles are stabilized by the solvents or the simple ions of the reducing agents or low-molecular-weight salts used. Surfactant-free synthesis of metal nanoparticles via photochemical-, ultrasonochemical-, and laser ablation-mediated synthesis methods is also described. Because of the effective utilization of their surfaces, metal nanoparticles prepared without surfactants, polymers, templates, or seeds are expected to exhibit high performance when used in catalysis (synthetic catalysis and electrocatalysis) and sensing (surface-enhanced Raman scattering (SERS)), surfaceassisted laser desorption/ionization-mass spectrometry (SALDI-MS)).

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Colloidal catalysis: the effect of sol size and concentration

Cited by 154 publications

References 1 publication

Shape-Tailored Colloidal Molecules Obtained by Self-Assembly of Model Gold Nanoparticles with Flexible Polyelectrolyte

Shape-Tailored Colloidal Molecules Obtained by Self-Assembly of Model Gold Nanoparticles with Flexible Polyelectrolyte

A New Catalytically Active Colloidal Platinum Nanocatalyst: The Multiarmed Nanostar Single Crystal

Surfactant-free solution-based synthesis of metallic nanoparticles toward efficient use of the nanoparticles’ surfaces and their application in catalysis and chemo-/biosensing

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