Interrogation of Nanoscale Silicon Dioxide/Water Interfaces via Hyper-Rayleigh Scattering

Vance, Fredrick W.; Lemon, Buford I.; Ekhoff, Jessica A.; Hupp, Joseph T.

doi:10.1021/jp9800261

Cited by 30 publications

(33 citation statements)

References 28 publications

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“…This work follows several recent reports of substantial HRS from nanocrystalline gold particle suspensions [7][8][9][10] and reports of SHG from highly concentrated gold nanoparticle samples [11,12]. HRS signals from gold nanoparticles were observed to exceed by factors of up to 10 5 those observed from suspensions of similarly sized wide bandgap semiconductor particles [13] and silicondioxide insulator particles [14]. The SHG study showed conclusively, via excitation profile measurements, that the nonlinear response is dramatically enhanced by resonance interactions with the gold plasmon band.…”

Section: Introductionsupporting

confidence: 89%

Hyper-Rayleigh scattering studies of silver, copper, and platinum nanoparticle suspensions

Johnson

Hupp

et al. 2002

Chemical Physics Letters

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142

109

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The optical frequency doubling properties of silver, copper, and platinum nanoparticles in aqueous solution are studied via hyper-Rayleigh scattering (HRS) spectroscopy. Substantial HRS responses are observed for silver and copper particles. The response is attributed to enhancement due to resonance of the nonlinearly scattered light with the particles' surface plasmon absorption band. Platinum particles, which lack visible-region plasmon absorption, do not display detectable HRS signals. The largest signals from silver particles are observed under conditions of two-photon resonance, qualitatively consistent with the predictions of available theory; smaller yet still impressive signals are observed under pre-and post-resonant conditions. Ó

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Section: Introductionsupporting

confidence: 89%

Hyper-Rayleigh scattering studies of silver, copper, and platinum nanoparticle suspensions

Johnson

Hupp

et al. 2002

Chemical Physics Letters

Self Cite

142

109

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“…[27][28][29]. The conflicting estimates of the ratios of silanol groups with different structural motifs [25][26][27][28][29] likely reflect the difficulty brought about by the tendency of liquid water to react with crystalline silica. [20] One indisputable experimental finding is that the silanol surface density is σ SiOH ≈ 4.6 nm −2 on well-soaked amorphous Oxygen, silicon, and hydrogen atoms are colored in yellow, red, and white, respectively.…”

Section: Introductionmentioning

confidence: 99%

“…[16,[22][23][24] On the other hand, the Q 2 :Q 3 ratio has also been described as either approximately 1:4 or 4:1, which has prompted assignment of the pK a =4.5 SiOH group to either Q 2 (Refs. 25,26) or Q 3 (Refs. [27][28][29].…”

Section: Introductionmentioning

confidence: 99%

Elucidating the Bimodal Acid−Base Behavior of the Water−Silica Interface from First Principles

2009

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Understanding the acid-base behavior of silica surfaces is critical for many nanoscience and bionano interface applications. Silanol groups (SiOH) on silica surfaces exhibit two acidity constants-one as acidic as vinegar-but their structural basis remains controversial. The atomic details of the more acidic silanol site govern not just the overall surface charge density at near neutral solution pH but also how ions and biomolecules interact with and bind to silica immersed in water. Using ab initio molecular dynamics simulations and multiple representative crystalline silica surfaces, we determine the deprotonation free energies of silanol groups with different structural motifs. We show that previously proposed motifs related to chemical connectivity or intersilanol hydrogen bonds do not yield high acidity. Instead, a plausible candiate for pK(a) = 4.5 silanol groups may be found in locally strained or defected regions with sparse silanol coverage. In the process, irreversible ring-opening reactions of strained silica trimer rings in contact with liquid water are observed.

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“…There are at least two types of silanol groups at the water/silica interface characterized by a dissociation p K a of 4.5–6.5 for about 20% of the silanol sites, and a p K a value of 8.5–9.0 for the remaining 80% (6–13). The p K a values were associated with the geminal and single silanols, respectively (14,15).…”

Section: Introductionmentioning

confidence: 99%

Water/Silica Nanoparticle Interfacial Kinetics of Sulfate, Hydrogen Phosphate, and Dithiocyanate Radicals

Caregnato

Bertolotti

González

et al. 2005

Photochem & Photobiology

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The values of the rate constants for the reactions of the sulfate (2.5 x 10(9) M(-1) s(-1)) and hydrogen phosphate (2.2 x 10(8) M(-1) s(-1)) radicals with silica nanoparticles are obtained by flash photolysis experiments with silica suspensions containing S(2)O(8)(2-) or P(2)O(8)(4-), respectively. The interaction of these radicals with the silica nanoparticles leads to formation of transients, probably adsorbed sulfate and hydrogen phosphate radicals, with absorption maxima at around 320 and 350 nm, respectively. A different mechanism takes place for the interaction of the less oxidizing dithiocyanate radicals with the silica nanoparticles. These radicals selectively react with the dissociated silanol groups of the nanoparticles with a rate constant at 298.2K of 7 x 10(7) M(-1) s(-1) (per mol of SiO(-) groups), and there is no evidence for their adsorption at the surface. All the results are discussed in terms of the Smoluchowski equation and redox potential of the inorganic radicals.

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Interrogation of Nanoscale Silicon Dioxide/Water Interfaces via Hyper-Rayleigh Scattering

Cited by 30 publications

References 28 publications

Hyper-Rayleigh scattering studies of silver, copper, and platinum nanoparticle suspensions

Hyper-Rayleigh scattering studies of silver, copper, and platinum nanoparticle suspensions

Elucidating the Bimodal Acid−Base Behavior of the Water−Silica Interface from First Principles

Water/Silica Nanoparticle Interfacial Kinetics of Sulfate, Hydrogen Phosphate, and Dithiocyanate Radicals

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