Chain Mechanism of Radical-Initiated Ligand Exchange in PtCl<sub>4</sub><sup>2-</sup> in Aqueous Solution

Janata, E.; Henglein, and Arnim; Ершов, Б. Г.

doi:10.1021/jp953027r

Cited by 12 publications

(9 citation statements)

References 7 publications

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“…It thus seems that an autocatalytic mechanism contributes to colloid formation, possibly via a catalyzed reduction of Au−III by the formaldehyde formed in eq 2. An autocatalytic mechanism in the radiolytic reduction of PtCl 4 2- has previously been found …”

Section: Discussionmentioning

confidence: 93%

Radiolytic Preparation of Ultrafine Colloidal Gold Particles in Aqueous Solution: Optical Spectrum, Controlled Growth, and Some Chemical Reactions

1999

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Orange-or yellow-orange-colored aqueous dispersions of ultrafine gold particles (∼2 nm) result from the γ-irradiation of deaerated solutions containing hydrolyzed AuCl4and poly(vinyl alcohol) or poly-(vinylpyrrolidone), respectively. The particles have a weak and very broad plasmon absorption band with maximum in the 490 to 500 nm range, i.e., at substantially shorter wavelengths than expected from classical Mie theory using bulk dielectric data; moreover, the specific UV absorption increases as the particles become smaller. The particles are used as seeds in the radiolytic reduction of added Au(CN)2to yield larger particles of any desired size and improved monodispersity. The particles partially react with oxygen. Chemisorption of 3-mercapto propionic acid strongly affects the electronics of the particles, as indicated by the changes in optical absorption. The early stages of AuCl4reduction are also investigated. The reduction occurs essentially in two steps: (1) formation, and (2) reduction of Au + . A 203-nm absorption band is tentatively attributed to Au + . Without further irradiation, Au + disappears thermally within hours to yield larger particles (20-70 nm).

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Section: Discussionmentioning

confidence: 93%

Radiolytic Preparation of Ultrafine Colloidal Gold Particles in Aqueous Solution: Optical Spectrum, Controlled Growth, and Some Chemical Reactions

1999

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“…Earlier, Creighton and Eadon calculated the optical absorption of platinum nanoparticles based on the Mie theory and demonstrated that a plasmon peak should appear at 215 nm . Experimentally, Henglein et al showed that a peak actually exists around 215 nm for nanoparticles prepared by the radiolytic reduction of PtCl 4 2– . , Nevertheless, until recently most of platinum particles that have been prepared were smaller than ∼10 nm and showed negligible absorption in the visible region. However, it was recently reported that Pt particles greater than 100 nm could be prepared under laboratory conditions .…”

Section: Introductionmentioning

confidence: 99%

Surface-Enhanced Raman Scattering of 4-Aminobenzenethiol in Nanogaps between a Planar Ag Substrate and Pt Nanoparticles

et al. 2011

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To determine how effectively transition metal nanoparticles can couple with a noble metal substrate to induce higher electromagnetic fields, we examined the surface-enhanced Raman scattering (SERS) characteristics of 4-aminobenzenethiol (4-ABT) positioned in the gaps formed by a flat Ag substrate and 20–150 nm Pt nanoparticles. Initially, no Raman peaks of 4-ABT could be identified when 4-ABT was self-assembled on a polished flat Ag substrate; however, Raman peaks could be seen by attaching Pt nanoparticles onto the pendent amine groups. Conversely, a higher Raman signal was observed when larger Pt nanoparticles were attached onto 4-ABT, regardless of the excitation wavelength. Moreover, a higher Raman signal was measured in response to excitation at 488 nm, followed by excitation at 514.5, 568, and 632.8 nm. Very similar size and excitation wavelength dependences were found from the 3-dimensional finite-difference time-domain simulation. Accordingly, the highest enhancement was achieved using ∼150 nm Pt particles at 488 nm excitation with an enhancement factor (EF) of 3.5 × 104 per Pt particle. However, the electromagnetic field enhancement observed was not in conformity with the UV/vis absorbance of ∼150 nm Pt nanoparticles, which suggested that higher EFs would be measured in the order of excitations at 632.8 > 568 > 514.5 > 488 nm. This discrepancy was attributed to the structure of Pt nanoparticles in that the 150 nm Pt particles were actually composed of 7 nm seed particles; thus, the electromagnetic interactions of individual Pt seed particles with the underlying Ag substrate occurred collectively, being more effective at shorter excitation wavelengths.

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“…Figure 1 shows the absorption spectra of an aqueous solution containing a 3:1 molar ratio of Pt/Pd (metal ions) along with PEG (stabilizer) and 2-propanol, as a function of the sonication time. Together with a strong absorption below 300 nm, the initial spectrum shows absorption bands centered at~325 and 390 nm likely arising from PtCl 4 2− and Pd(CH 3 COO) 2 species, respectively [39,40]. Within 1 h of sonication, the above-mentioned absorption bands disappeared, and a clear dark brown solution was obtained.…”

Section: Resultsmentioning

confidence: 98%

Sonochemical synthesis of graphene oxide supported Pt–Pd alloy nanocrystals as efficient electrocatalysts for methanol oxidation

Neppolian

Sáez

González-Garcı́a

et al. 2014

J Solid State Electrochem

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Pt-Pd bimetallic nanoparticles supported on graphene oxide (GO) nanosheets were prepared by a sonochemical reduction method in the presence of polyethylene glycol as a stabilizing agent. The synthetic method allowed for a fine tuning of the particle composition without significant changes in their size and degree of aggregation. Detailed characterization of GO-supported Pt-Pd catalysts was carried out by transmission electron microscopy (TEM), AFM, XPS, and electrochemical techniques. Uniform deposition of Pt-Pd nanoparticles with an average diameter of 3 nm was achieved on graphene nanosheets using a novel dual-frequency sonication approach. GO-supported bimetallic catalyst showed significant electrocatalytic activity for methanol oxidation. The influence of different molar compositions of Pt and Pd (1:1, 2:1, and 3:1) on the methanol oxidation efficiency was also evaluated. Among the different Pt/Pd ratios, the 1:1 ratio material showed the lowest onset potential and generated the highest peak current density. The effect of catalyst loading on carbon paper (working electrode) was also studied. Increasing the catalyst loading beyond a certain amount lowered the catalytic activity due to the aggregation of metal particle-loaded GO nanosheets.

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Chain Mechanism of Radical-Initiated Ligand Exchange in PtCl₄^2- in Aqueous Solution

Cited by 12 publications

References 7 publications

Radiolytic Preparation of Ultrafine Colloidal Gold Particles in Aqueous Solution: Optical Spectrum, Controlled Growth, and Some Chemical Reactions

Radiolytic Preparation of Ultrafine Colloidal Gold Particles in Aqueous Solution: Optical Spectrum, Controlled Growth, and Some Chemical Reactions

Surface-Enhanced Raman Scattering of 4-Aminobenzenethiol in Nanogaps between a Planar Ag Substrate and Pt Nanoparticles

Sonochemical synthesis of graphene oxide supported Pt–Pd alloy nanocrystals as efficient electrocatalysts for methanol oxidation

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Chain Mechanism of Radical-Initiated Ligand Exchange in PtCl42- in Aqueous Solution

Cited by 12 publications

References 7 publications

Radiolytic Preparation of Ultrafine Colloidal Gold Particles in Aqueous Solution: Optical Spectrum, Controlled Growth, and Some Chemical Reactions

Radiolytic Preparation of Ultrafine Colloidal Gold Particles in Aqueous Solution: Optical Spectrum, Controlled Growth, and Some Chemical Reactions

Surface-Enhanced Raman Scattering of 4-Aminobenzenethiol in Nanogaps between a Planar Ag Substrate and Pt Nanoparticles

Sonochemical synthesis of graphene oxide supported Pt–Pd alloy nanocrystals as efficient electrocatalysts for methanol oxidation

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Chain Mechanism of Radical-Initiated Ligand Exchange in PtCl₄^2- in Aqueous Solution