Generation of Chemisorbed Benzyl Radicals on Silica Nanoparticles

Arce, Valeria B.; Rosso, Janina A.; Oliveira, Fernando J.V.E.; Airoldi, Cláudio; Soria, Delia Beatriz; González, Mónica C.; Allegretti, Patricia Ercilia; Mártire, Daniel O.

doi:10.1111/j.1751-1097.2010.00810.x

Cited by 5 publications

(14 citation statements)

References 41 publications

(54 reference statements)

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“…The silica nanoparticles modified with n-butanol and benzyl alcohol used for comparison purposes were synthesized and characterized as described elsewhere. 3,8 Acetonitrile or 1 : 1 mixtures of acetonitrile-aqueous phosphate buffer ( pH = 6.4) were used as the solvents for the timeresolved experiments.…”

Section: Synthesis Of the Nanoparticlesmentioning

confidence: 99%

“…These samples were prepared by employing the method reported elsewhere. 3,8 The percentages of organic groups (%OG) determined for the nanoparticles modified with n-butanol and benzyl alcohol from the values of SSA of these samples were 6 ± 3 and 10 ± 3, respectively.…”

Section: Toxicity Assaysmentioning

confidence: 99%

“…A reaction route leading to the formation of silica chemisorbed benzyl radicals can also be neglected here because these radicals show an absorption maximum at 320 nm. 8 The 4-methoxybenzyl radical also shows an absorption maximum at 320 nm in solution. 44 The decay rate of the transient measured here at 380 nm increases with increasing O 2 concentration.…”

Section: Photochemical Experimentsmentioning

confidence: 99%

“…Since we are interested in evaluating the effect of alcohol adsorption on the surface, we determined the surface area, 7 and the number of modified silanols. 2,3,8 The characterization also includes toxicity assays performed with suspensions of the particles. These measurements appear sufficient to evaluate both the biocidal effects of these hybrid materials on microorganisms and their secondary effects when contained in surface and drinking water.…”

Section: Introductionmentioning

confidence: 99%

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Triplet state of 4-methoxybenzyl alcohol chemisorbed on silica nanoparticles

Arce

Bertolotti

Oliveira

et al. 2012

Photochem Photobiol Sci

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The knowledge of photochemical kinetics in colloidal systems is important in understanding environmental photochemistry on dispersed solid surfaces. As model materials for the chemically sorbed organic compounds present in natural environments, modified silica nanoparticles (NPs) were obtained here by condensation of the silanol groups of fumed silica nanoparticles with 4-methoxybenzyl alcohol. These particles were characterized by different techniques. To evaluate their toxicity, the inhibition of the natural luminescence emission of the marine bacterium Vibrio fischeri in suspensions of the particles was measured. Laser flash-photolysis experiments (λ exc = 266 nm) performed with NP suspensions in acetonitrile-aqueous phosphate buffer mixtures showed the formation of the lowest triplet excited state of the chemisorbed organic groups (λ max = 390 nm). DFT calculations of the absorption spectrum of this radical support the assignment. From the calculated triplet energy, a thermodynamically favorable energy transfer from these triplet states to oxygen to yield singlet molecular oxygen is predicted. A value of 0.09 was measured for the quantum yield of singlet molecular oxygen generation by air-saturated suspensions of the nanoparticles in the mixture of solvents acetonitrile-aqueous phosphate buffer. The quantum yield of singlet molecular oxygen generation by the free 4-methoxybenzyl alcohol in the same solvent is 0.31. † Dedicated to Prof. Kurt Schaffner on the occasion of his 80th birthday. ‡ Electronic supplementary information (ESI) available: TEM images, 29 Si NMR in solid state of the modified nanoparticles. Percentage of luminescence inhibition vs. the concentration of benzyl alcohol. FTIR spectra of 4-methoxybenzyl alcohol experimental and simulated. Experimental IR wavenumbers for NP and 4-methoxybenzyl alcohol. See

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Section: Synthesis Of the Nanoparticlesmentioning

confidence: 99%

Section: Toxicity Assaysmentioning

confidence: 99%

Section: Photochemical Experimentsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Triplet state of 4-methoxybenzyl alcohol chemisorbed on silica nanoparticles

Arce

Bertolotti

Oliveira

et al. 2012

Photochem Photobiol Sci

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“…La disminución del área superficial específica de las partículas derivatizadas con grupos orgánicos se ha observado en varios sistemas [Arce 2010b, Jitianu 2002. Este efecto se debe a que las moléculas de nitrógeno se adsorben preferentemente sobre la superficie oxidada de las nanopartículas y se observa una débil adsorción sobre la superficie orgánica comparada con la de la superficie de sílice desnuda.…”

Section: Adsorción De N 2 Y O 2 Sobre Las Nanopartículasunclassified

Desarrollo de nanopartículas de silicio como potenciales marcadores luminiscentes y agentes terapéuticos en sistemas biológicos

Portolés¹,

Manuel²

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Se plantea como hipótesis de esta tesis que: “las nanopartículas de silicio tienen potencial utilidad como marcadores biológicos y/o agentes terapéuticos”. Para desarrollarla, en una primera etapa se realizó la síntesis de las nanopartículas con las cuales se llevaron a cabo todos los estudios posteriores. Para este objetivo se evaluaron distintos métodos de síntesis eligiendo el más adecuado para nuestra accesibilidad de equipos y adaptándolo a nuestros requerimientos específicos. Una vez obtenidas las nanopartículas se procedió a la modificación superficial con distintos agentes químicos, determinándose su adecuado recubrimiento y distribución de tamaños. Posteriormente se procedió a la caracterización de sus propiedades fotofísicas en función de los diferentes recubrimientos superficiales y del solvente en régimen por excitación mono- y bifotónica. Se analizó la capacidad de las partículas de generar especies reactivas de oxígeno y de reducir diferentes especies químicas mediadas por la luz. Asimismo, se han planteado los mecanismos por los que se producen estos fenómenos. Paralelamente a los estudios experimentales se han realizado cálculos teóricos para obtener las configuraciones geométricas más estables en función de su multiplicidad y su recubrimiento con átomos de distintos elementos. Se calculó el espectro electrónico UV-Vis y el espectro vibracional de las partículas de tamaños y recubrimientos similares a las obtenidas experimentalmente. Se evaluó la toxicidad de las nanopartículas recubiertas con metacrilato de metilo en células C6 de glioma de rata en función de la concentración de partículas, del tiempo de incubación y de irradiación en el IR.

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Strategies to Passivate Brønsted Acidity in Nb-TUD-1 Enhance Hydrogen Peroxide Utilization and Reduce Metal Leaching during Ethylene Epoxidation

Maiti¹,

Ramanathan²,

Thompson³

et al. 2017

Ind. Eng. Chem. Res.

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The passivation of Brønsted acid sites in Nb-TUD-1 to improve H 2 O 2 utilization and resistance to Nb leaching during the liquid-phase epoxidation of ethylene under mild operating conditions (35 °C and 50 bar) was studied. Our first strategy was to create hydrophobic ion pairs through the base treatment of Nb-TUD-1 using two organic bases, namely, tetraethylammonium hydroxide and diisopropylethylamine. Although these systems significantly enhanced H 2 O 2 utilization toward ethylene oxide (EO) formation (70% and 90%, respectively), resistance to metal leaching was only moderately improved. We therefore investigated an alternative strategy using four different covalently bound capping groups, namely, methyl (Me), trimethylsilyl (TMS), tert-butyl (t-Bu), and benzyl (Bn), ranging from moderate to high hydrolytic stability. The catalyst capped using the benzyl group, Bn-Nb(40), showed the best performance in terms of significantly improved H 2 O 2 utilization toward EO formation (∼60−71%) and reduced metal leaching (∼3%). The EO selectivity was >98%. Further, the structure of the Bn-Nb(40) catalyst was found to be stable under reaction conditions even after several recycle runs, thus confirming its potential as a viable epoxidation catalyst.

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Generation of Chemisorbed Benzyl Radicals on Silica Nanoparticles

Cited by 5 publications

References 41 publications

Triplet state of 4-methoxybenzyl alcohol chemisorbed on silica nanoparticles

Triplet state of 4-methoxybenzyl alcohol chemisorbed on silica nanoparticles

Desarrollo de nanopartículas de silicio como potenciales marcadores luminiscentes y agentes terapéuticos en sistemas biológicos

Strategies to Passivate Brønsted Acidity in Nb-TUD-1 Enhance Hydrogen Peroxide Utilization and Reduce Metal Leaching during Ethylene Epoxidation

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