Analysis of Hybrid Silica Materials with the Aid of Conventional NMR and GC/MS

Mello, Rossella; Olmos, Andrea; Varea, Teresa; González‐Núñez, María Elena

doi:10.1021/ac801248m

Cited by 13 publications

(30 citation statements)

References 38 publications

(17 reference statements)

Supporting

Mentioning

Contrasting

Order By: Relevance

“…52,53 100 mg silica 10 or 15 - 18 in 2 mL distilled water was added to 2 mL 40% aqueous HF with stirring in a Teflon container at 0 °C. Dissolution of the silica occurred after ~1 h, after which the mixture was added to 2 mL CH 2 Cl 2 with stirring for 15 min at 0 °C.…”

Section: Methodsmentioning

confidence: 99%

Fluorine End-Capped Optical Fibers for Photosensitizer Release and Singlet Oxygen Production

et al. 2012

View full text Add to dashboard Cite

The usefulness of a fiber optic technique for generating singlet oxygen and releasing the pheophorbide photosensitizer has been increased by the fluorination of the porous Vycor glass tip. Singlet oxygen emerges through the fiber tip with 669-nm light and oxygen, releasing the sensitizer molecules upon a [2 + 2] addition of singlet oxygen with the ethene spacer and scission of a dioxetane intermediate. Switching from a non-fluorinated to a fluorinated glass tip led to a clear reduction of the adsorbtive affinity of the departing sensitizer with improved release into homogeneous toluene solution and bovine tissue. But no difference was found in water since the sensitizer was insoluble. High surface coverage of the nonafluorohexylsilane enhanced the cleavage efficiency by 15% at the ethene site. The fluorosilane groups also caused crowding and seemed to reduce access of 1O2 to the ethene site, which attenuated the total quenching rate constant kT, although there was less wasted 1O2 (from surface physical quenching) at the fluorosilane-coated than the native SiOH silica. The observations support a quenching mechanism that the replacement of the SiOH groups for the fluorosilane C-H and C-F groups enhanced the 1O2 lifetime at the fiber tip interface due to less efficient electronic-to-vibronic energy transfer.

show abstract

Section: Methodsmentioning

confidence: 99%

Fluorine End-Capped Optical Fibers for Photosensitizer Release and Singlet Oxygen Production

et al. 2012

View full text Add to dashboard Cite

show abstract

“…For example, in the case of 1b , it was shown that 0.54 mmol of silanol groups/g of 1b reacted with VDMCS. This value was lower than that of mesoporous MCM‐41 by one order 28. It seems that this result originates from the difference of the specific surface area value between two of the materials.…”

Section: Resultsmentioning

confidence: 71%

“…Recently, Mello et al reported an analytical method for organically modified silica materials using NMR and GC/MS 28. This method involves dissolving the organically modified silicas either in a concentrated solution of sodium hydroxide or in a solution of hydrogen fluoride, and provides immediate information concerning both the amount and chemical composition of the organic moiety anchored onto the silica surface.…”

Section: Introductionmentioning

confidence: 99%

Quantitative ¹H NMR analysis of reacted silanol groups in silica nanoparticles chemically modified with monochlorosilanes

Nakahara

Takeuchi

Yokoyama

et al. 2011

Surface & Interface Analysis

View full text Add to dashboard Cite

Quantitative analysis of reacted silanol groups in silica nanoparticles modified chemically with monochlorosilanes was performed by 1 H NMR after treatment with cesium fluoride. Silica nanoparticles were modified chemically by the reaction between the silanol groups and monochlorosilanes, and the structure of the organic moiety anchored onto the silica surface was confirmed with solid-state 13 C NMR. As monochlorosilanes react with silanol groups at 1 : 1 ratio unlike di-or trichlorosilanes, the number of the silanes introduced into silica nanoparticles equals that of reacted silanol groups. Organically modified silica nanoparticles were dissolved using cesium fluoride, and the amount of the soluble organic compounds originated from the introduced silanes was determined by a 1 H NMR internal standard method using pyrene as the reference. Those values determined by 1 H NMR were in good agreement with those determined by elemental analysis. Thus, the number of reacted silanol groups per one particle was calculated on the basis of the results obtained by the 1 H NMR method, and the values were highly dependent on the steric structure of the introduced silanes.

show abstract

“…The new hybrid material 3 was fully characterized by a combination of FTIR, NMR, and X‐ray photoelectron spectroscopy (XPS). When added to a solution of 4.9 M NaOH in D 2 O, it was observed that 3 is not resistant to the strongly basic conditions required to dissolve the silica gel particles 13b. However, we found that careful treatment of 3 with a 4.9 M NaOH in D 2 O solution containing excess sodium borohydride (NaBH 4 ) gives a well‐defined 19 F NMR spectrum (Supporting Information, Figure S8).…”

Section: Resultsmentioning

confidence: 95%

Dioxirane‐Mediated Heterogeneous Epoxidations with Potassium Caroate: A Solid Catalyst Bearing Anchored Ketone Moieties

D’Accolti¹,

Annese²,

Riccardis³

et al. 2012

Eur J Org Chem

View full text Add to dashboard Cite

A new hybrid material (3) consisting of trifluoromethyl ketone (TFMK) moieties, immobilized on silica through an appropriate spacer, was synthesized and characterized. Lacking easily oxidizable functionalities in the spacer chain, this material proved to be an excellent catalyst in heterogeneous epoxidations with potassium caroate (KHSO5), surpassing other reported catalysts in performance and stability. The efficiency of silica‐supported catalyst 3 could be assessed upon carrying out the selective dioxirane‐mediated epoxidation of representative alkenes in high yields. The solid catalyst could then be recovered and reused in a number of consecutive oxidation cycles.

show abstract

Analysis of Hybrid Silica Materials with the Aid of Conventional NMR and GC/MS

Cited by 13 publications

References 38 publications

Fluorine End-Capped Optical Fibers for Photosensitizer Release and Singlet Oxygen Production

Fluorine End-Capped Optical Fibers for Photosensitizer Release and Singlet Oxygen Production

Quantitative ¹H NMR analysis of reacted silanol groups in silica nanoparticles chemically modified with monochlorosilanes

Dioxirane‐Mediated Heterogeneous Epoxidations with Potassium Caroate: A Solid Catalyst Bearing Anchored Ketone Moieties

Contact Info

Product

Resources

About

Analysis of Hybrid Silica Materials with the Aid of Conventional NMR and GC/MS

Cited by 13 publications

References 38 publications

Fluorine End-Capped Optical Fibers for Photosensitizer Release and Singlet Oxygen Production

Fluorine End-Capped Optical Fibers for Photosensitizer Release and Singlet Oxygen Production

Quantitative 1H NMR analysis of reacted silanol groups in silica nanoparticles chemically modified with monochlorosilanes

Dioxirane‐Mediated Heterogeneous Epoxidations with Potassium Caroate: A Solid Catalyst Bearing Anchored Ketone Moieties

Contact Info

Product

Resources

About

Quantitative ¹H NMR analysis of reacted silanol groups in silica nanoparticles chemically modified with monochlorosilanes