Shape-Controlled Syntheses of Gold Nanoprisms and Nanorods Influenced by Specific Adsorption of Halide Ions

Ha, Tai Hwan; Koo, Hee-Joon; Chung, Bong Hyun

doi:10.1021/jp066454l

Cited by 374 publications

(423 citation statements)

References 65 publications

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“…A similar result on plate formation promoted with the addition of a small amount of halide ion (especially, iodide ion) in a growth solution has been reported in the presence of cetyltrimethylammonium bromide (CTAB). [34] 3.3 Effect of temperature on particle size and shape Finally, let us examine how temperature affects the size and shape of gold nanoparticles ultrasonically prepared in the absence of any stabilizing and capping agents.…”

Section: Resultsmentioning

confidence: 99%

Surfactant- and reducer-free synthesis of gold nanoparticles in aqueous solutions

Sakai

Enomoto

Torigoe

et al. 2009

Colloids and Surfaces A: Physicochemical and Engineering Aspect

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We report here the surfactant-and reducer-free synthesis of gold nanoparticles from an aqueous hydrogen tetrachloroaurate (III) tetrahydrate (HAuCl 4 ·4H 2 O) solution using a high-frequency (950 kHz) ultrasound (in the absence of any stabilizing, capping and reducing agents). In particular, size, shape and stability of gold nanoparticles prepared by the 950 kHz ultrasound irradiation (sonication) for 8 min in the surfactant-free aqueous solutions were examined in terms of AuCl 4 -concentration (in the range of 0.01-0.1 mM), additional salts (NaCl, HCl and NaOH) and temperature (in the range of 4-60 ˚C). We found that higher AuCl 4 -concentration promoted particle growth (size increase) and plate formation.In addition, the plate formation was enhanced with the addition of NaCl or HCl (but not NaOH). This is most likely due to the AuCl 4 -reduction on a certain crystal facets (e.g., (110) facets) caused by the adsorption of Cl -ions on specific crystal facets (e.g., (111) facets).Furthermore, we revealed that the temperature elevated above 50 ˚C led to the formation of spherical gold nanoparticles with the diameter of 20-60 nm from a 0.1 mM AuCl 4 -aqueous solution while triangular plates formed coexisting with spherical nanoparticles below 50 ˚C.

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Section: Resultsmentioning

confidence: 99%

Surfactant- and reducer-free synthesis of gold nanoparticles in aqueous solutions

Sakai

Enomoto

Torigoe

et al. 2009

Colloids and Surfaces A: Physicochemical and Engineering Aspect

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“…54 In general, it is accepted that the CTAB adsorption process on a gold surface occurs via the strong gold-bromide interactions. 55 Our simulation of the adsorption of CTAB R micelles on gold surfaces shows a pattern of adjacent cylindrical micelles anchored on gold (see Figure 8). This same trend was already reported by Meena and Sulpizi.…”

Section: Simulation Of Ctab R Adsorption On a Gold Surfacementioning

confidence: 89%

Molecular Dynamics Simulations of Cetyltrimethylammonium Bromide (CTAB) Micelles and their Interactions with a Gold Surface in Aqueous Solution

Silva¹,

Dias²,

Hora³

et al. 2017

J. Braz. Chem. Soc.

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Surfactants are molecular structures with remarkable physicochemical properties and applications. Most of their characteristics are due to their ability to promote aggregation and interactions with different interfaces. The scarcity of theoretical studies dedicated to evaluating the forces involved in these interactions prompted us to propose other models capable of reproducing the experimental data in better ways. We carried out molecular dynamics (MD) simulations to obtain a model for cetyltrimethylammonium bromide (CTAB), selected from gromos54a7 force field parameters, that better describes most of its behaviors in aqueous solution (micellar structure, counterion dissociation, etc.) and its adsorption pattern on a gold surface. The parameters adopted for one of the models were able to mimic several characteristics suggested by experimental measurements of the CTAB micelles, as well their adsorption pattern on a gold surface. Indeed, this model was able to obtain quasi-spherical micelles, as well as a pattern of adjacent cylindrical micelles with alkyl chain interactions on a gold surface.Keywords: molecular dynamics, micelles, interface interaction, cetyltrimethylammonium bromide, gold IntroductionSurfactants are a class of compounds containing a polar group, charged or neutral, attached to a long hydrophobic tail.1,2 These are remarkably versatile compounds with a broad variety of important applications in the pharmaceutical, medical, and food industries and for nanomaterial synthesis.3,4 Above a certain temperature in solution (the Krafft temperature), surfactants tend to aggregate to minimize unfavorable interactions between the surfactants and the surrounding environment. 5 The minimum concentration required for surfactant aggregation is defined as the critical micellar concentration (CMC), and most of the characteristics of these aggregates are controlled by factors such as the solvent type, chemical structure of the surfactant, and solution conditions (e.g., concentration, temperature, presence of additives, and ionic strength). 6Variations of these factors yield aggregates with different morphologies such as spherical or ellipsoidal micelles, cylindrical or thread-like micelles, disk-like micelle, membranes and vesicles.7 These self-assembled structures have been characterized by a number of techniques, such as dynamic light scattering (DLS), 8 nuclear magnetic resonance (NMR), 9,10 fluorescence spectroscopy, 11 quasielastic neutron scattering (QENS), 12,13 small-angle X-ray scattering (SAXS), 14,15 and small-angle neutron scattering (SANS). 16,17 Computational simulations have also been employed to explore the structures and dynamical behaviors of micelles for different surfactants. 18Considering that no holes exist within a micelle, its radius is estimated as the maximum extension of a hydrocarbon chain and can be evaluated by using the following equation:where l max is the maximum length in nm and n C is the number of carbon atoms in the chain. 19 Indeed, under the previously mentioned conditions, ...

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“…As Cl − has a lower affinity to gold than Br − , 28 Cl − would preferentially adsorb on the gold surface to create a negatively charged layer, where CTA + could subsequently bind through electrostatic interactions. 29 Pre-adsorbed Cl − cannot screen the selective adsorption of CTA + on the high-index facets because of its lower affinity compared with Br − . Binding of the large [NMe3] + head group of CTA + (diameter = 0.814 nm) and its associated long alkyl tail can be more easily accommodated on less closely packed high-index planes than on low-index planes.…”

Section: Energy Storage and Conversion D Su Et Almentioning

confidence: 99%

Gold nanocrystals with variable index facets as highly effective cathode catalysts for lithium–oxygen batteries

Dou

Wang

2015

NPG Asia Mater

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Cathode catalysts are the key factor in improving the electrochemical performance of lithium-oxygen (Li-O 2 ) batteries via their promotion of the oxygen reduction and oxygen evolution reactions (ORR and OER). Generally, the catalytic performance of nanocrystals (NCs) toward ORR and OER depends on both composition and shape. Herein, we report the synthesis of polyhedral Au NCs enclosed by a variety of index facets: cubic gold (Au) NCs enclosed by {100} facets; truncated octahedral Au NCs enclosed by {100} and {110} facets; and trisoctahedral (TOH) Au NCs enclosed by 24 high-index {441} facets, as effective cathode catalysts for Li-O 2 batteries. All Au NCs can significantly reduce the charge potential and have high reversible capacities. In particular, TOH Au NC catalysts demonstrated the lowest charge-discharge overpotential and the highest capacity of~20 298 mA h g − 1 . The correlation between the different Au NC crystal planes and their electrochemical catalytic performances was revealed: high-index facets exhibit much higher catalytic activity than the low-index planes, as the high-index planes have a high surface energy because of their large density of atomic steps, ledges and kinks, which can provide a high density of reactive sites for catalytic reactions. INTRODUCTIONThe lithium-oxygen (Li-O 2 ) battery is currently the subject of much scientific investigation as the power source for electric vehicles because of its high energy density (2-3 kWh kg − 1 ). 1 Unlike the intercalation reactions of Li-ion batteries, 2 the reaction mechanism in a Li-O 2 cell involves an oxygen reduction reaction (ORR) in the discharge process and an oxygen evolution reaction (OER) in the charge process, during which, molecular O 2 reacts reversibly with Li + ions (Li + + O 2 +2e − ↔ Li 2 O 2 , with an equilibrium voltage of 2.96 V vs. Li). 3 The performance of Li-O 2 batteries is constrained by several serious issues, such as poor cycling stability, 4 electrolyte instability, 5 low-rate capability 6 and low round-trip efficiencies, 1 mainly resulting from the high overpotential on charge. 7 Recently, it was found that the catalyst and the proper non-aqueous electrolyte are the key factors to address these problems. 8 Therefore, various electrocatalysts, including carbons, metal oxides, metal nitrides and precious metals have been examined as the cathode catalysts in Li-O 2 cells to lower the charge overpotential. 9 It was reported that the use of catalysts can decrease the charge potential tõ 3.8 from~4.2 V. 10 It has been shown, however, that the theoretical overcharge potential for a Li 2 O 2 film is only 0.2 V, if there are no limitations on charge transport through Li 2 O 2 to the Li 2 O 2 -electrolyte interface. 11 Therefore, it is possible to further lower the charge potential. Moreover, a fundamental understanding of how to resolve the high overpotential on charge and the mechanisms of both ORR and OER, respectively in non-aqueous electrolytes are important for developing Li-O 2 batteries.

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Shape-Controlled Syntheses of Gold Nanoprisms and Nanorods Influenced by Specific Adsorption of Halide Ions

Cited by 374 publications

References 65 publications

Surfactant- and reducer-free synthesis of gold nanoparticles in aqueous solutions

Surfactant- and reducer-free synthesis of gold nanoparticles in aqueous solutions

Molecular Dynamics Simulations of Cetyltrimethylammonium Bromide (CTAB) Micelles and their Interactions with a Gold Surface in Aqueous Solution

Gold nanocrystals with variable index facets as highly effective cathode catalysts for lithium–oxygen batteries

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